diff --git a/lib/esp-knx-ip-async-udp/esp-knx-ip-webserver.cpp b/lib/esp-knx-ip-async-udp/esp-knx-ip-webserver.cpp
index af981b78d..bdbc013fd 100644
--- a/lib/esp-knx-ip-async-udp/esp-knx-ip-webserver.cpp
+++ b/lib/esp-knx-ip-async-udp/esp-knx-ip-webserver.cpp
@@ -41,7 +41,9 @@ void ESPKNXIP::__handle_root()
           break;
         case FEEDBACK_TYPE_FLOAT:
           m += F("<span class='input-group-text'>");
+          m += feedbacks[i].options.float_options.prefix;
           m += String(*(float *)feedbacks[i].data, feedbacks[i].options.float_options.precision);
+          m += feedbacks[i].options.float_options.suffix;
           m += F("</span>");
           break;
         case FEEDBACK_TYPE_BOOL:
@@ -52,7 +54,9 @@ void ESPKNXIP::__handle_root()
         case FEEDBACK_TYPE_ACTION:
           m += F("<input class='form-control' type='hidden' name='id' value='");
           m += i;
-          m += F("' /><div class='input-group-append'><button type='submit' class='btn btn-primary'>Do this</button></div>");
+          m += F("' /><div class='input-group-append'><button type='submit' class='btn btn-primary'>");
+          m += feedbacks[i].options.action_options.btn_text;
+          m += F("</button></div>");
           break;
       }
       m += F("</div></div></div>");
@@ -67,6 +71,12 @@ void ESPKNXIP::__handle_root()
   {
     for (uint8_t i = 0; i < registered_callback_assignments; ++i)
     {
+      // Skip empty slots
+      if ((callback_assignments[i].slot_flags & SLOT_FLAGS_USED) == 0)
+      {
+        continue;
+      }
+      // Skip disabled callbacks
       if (callbacks[callback_assignments[i].callback_id].cond && !callbacks[callback_assignments[i].callback_id].cond())
       {
         continue;
@@ -105,6 +115,12 @@ void ESPKNXIP::__handle_root()
     m += F("<select class='form-control' name='cb'>");
     for (callback_id_t i = 0; i < registered_callbacks; ++i)
     {
+      // Skip empty slots
+      if ((callbacks[i].slot_flags & SLOT_FLAGS_USED) == 0)
+      {
+        continue;
+      }
+      // Skip disabled callbacks
       if (callbacks[i].cond && !callbacks[i].cond())
       {
         continue;
@@ -295,7 +311,7 @@ void ESPKNXIP::__handle_register()
       goto end;
     }
 
-    if (cb >= registered_callbacks)
+    if (!__callback_is_id_valid(cb))
     {
       DEBUG_PRINTLN(F("Invalid callback id"));
       goto end;
@@ -319,7 +335,7 @@ void ESPKNXIP::__handle_delete()
     DEBUG_PRINT(id);
     DEBUG_PRINTLN(F(""));
 
-    if (id >= registered_callback_assignments)
+    if (id >= registered_callback_assignments || (callback_assignments[id].slot_flags & SLOT_FLAGS_USED) == 0)
     {
       DEBUG_PRINTLN(F("ID wrong"));
       goto end;
diff --git a/lib/esp-knx-ip-async-udp/esp-knx-ip.cpp b/lib/esp-knx-ip-async-udp/esp-knx-ip.cpp
index 8bdca1edb..35b9c5014 100644
--- a/lib/esp-knx-ip-async-udp/esp-knx-ip.cpp
+++ b/lib/esp-knx-ip-async-udp/esp-knx-ip.cpp
@@ -6,7 +6,21 @@
 
 #include "esp-knx-ip.h"
 
-ESPKNXIP::ESPKNXIP() : server(nullptr), registered_callback_assignments(0), registered_callbacks(0), registered_configs(0), registered_feedbacks(0)
+char const *string_defaults[] =
+{
+  "Do this",
+  "True",
+  "False",
+  ""
+};
+
+ESPKNXIP::ESPKNXIP() : server(nullptr),
+                      registered_callback_assignments(0),
+                      free_callback_assignment_slots(0),
+                      registered_callbacks(0),
+                      free_callback_slots(0),
+                      registered_configs(0),
+                      registered_feedbacks(0)
 {
   DEBUG_PRINTLN();
   DEBUG_PRINTLN("ESPKNXIP starting up");
@@ -27,65 +41,65 @@ void ESPKNXIP::load()
   restore_from_eeprom();
 }
 
-void ESPKNXIP::start(ESP8266WebServer *srv, bool espknxip_webpage)
+void ESPKNXIP::start(ESP8266WebServer *srv)
 {
   server = srv;
-  if (espknxip_webpage) { __start_espknxip_webpage(); }
   __start();
 }
 
 void ESPKNXIP::start()
 {
   server = new ESP8266WebServer(80);
-  __start_espknxip_webpage();
   __start();
 }
 
-void ESPKNXIP::__start_espknxip_webpage()
-{
-  server->on(ROOT_PREFIX, [this](){
-    __handle_root();
-  });
-  server->on(__ROOT_PATH, [this](){
-    __handle_root();
-  });
-  server->on(__REGISTER_PATH, [this](){
-    __handle_register();
-  });
-  server->on(__DELETE_PATH, [this](){
-    __handle_delete();
-  });
-  server->on(__PHYS_PATH, [this](){
-    __handle_set();
-  });
-#if !DISABLE_EEPROM_BUTTONS
-  server->on(__EEPROM_PATH, [this](){
-    __handle_eeprom();
-  });
-#endif
-  server->on(__CONFIG_PATH, [this](){
-    __handle_config();
-  });
-  server->on(__FEEDBACK_PATH, [this](){
-    __handle_feedback();
-  });
-#if !DISABLE_RESTORE_BUTTON
-  server->on(__RESTORE_PATH, [this](){
-    __handle_restore();
-  });
-#endif
-#if !DISABLE_REBOOT_BUTTON
-  server->on(__REBOOT_PATH, [this](){
-    __handle_reboot();
-  });
-#endif
-  server->begin();
-}
-
 void ESPKNXIP::__start()
 {
+  if (server != nullptr)
+  {
+    server->on(ROOT_PREFIX, [this](){
+      __handle_root();
+    });
+    server->on(__ROOT_PATH, [this](){
+      __handle_root();
+    });
+    server->on(__REGISTER_PATH, [this](){
+      __handle_register();
+    });
+    server->on(__DELETE_PATH, [this](){
+      __handle_delete();
+    });
+    server->on(__PHYS_PATH, [this](){
+      __handle_set();
+    });
+#if !DISABLE_EEPROM_BUTTONS
+    server->on(__EEPROM_PATH, [this](){
+      __handle_eeprom();
+    });
+#endif
+    server->on(__CONFIG_PATH, [this](){
+      __handle_config();
+    });
+    server->on(__FEEDBACK_PATH, [this](){
+      __handle_feedback();
+    });
+#if !DISABLE_RESTORE_BUTTON
+    server->on(__RESTORE_PATH, [this](){
+      __handle_restore();
+    });
+#endif
+#if !DISABLE_REBOOT_BUTTON
+    server->on(__REBOOT_PATH, [this](){
+      __handle_reboot();
+    });
+#endif
+    server->begin();
+  }
+
   udp.listenMulticast(MULTICAST_IP, MULTICAST_PORT);
-  udp.onPacket([this](AsyncUDPPacket &packet) { __loop_knx(packet); });
+  udp.onPacket([this](AsyncUDPPacket &packet) {
+    DEBUG_PRINTLN("got packet");
+    __loop_knx(packet); });
 }
 
 void ESPKNXIP::save_to_eeprom()
@@ -139,6 +153,26 @@ void ESPKNXIP::restore_from_eeprom()
   for (uint8_t i = 0; i < MAX_CALLBACK_ASSIGNMENTS; ++i)
   {
     EEPROM.get(address, callback_assignments[i].address);
+    if (callback_assignments[i].address.value != 0)
+    {
+      // if address is not 0/0/0 then mark slot as used
+      callback_assignments[i].slot_flags |= SLOT_FLAGS_USED;
+      DEBUG_PRINTLN("used slot");
+    }
+    else
+    {
+      // if address is 0/0/0, then we found a free slot, yay!
+      // however, only count those slots, if we have not reached registered_callback_assignments yet
+      if (i < registered_callback_assignments)
+      {
+        DEBUG_PRINTLN("free slot before reaching registered_callback_assignments");
+        free_callback_assignment_slots++;
+      }
+      else
+      {
+        DEBUG_PRINTLN("free slot");
+      }
+    }
     address += sizeof(address_t);
   }
   for (uint8_t i = 0; i < MAX_CALLBACK_ASSIGNMENTS; ++i)
@@ -188,68 +222,106 @@ callback_assignment_id_t ESPKNXIP::__callback_register_assignment(address_t addr
   if (registered_callback_assignments >= MAX_CALLBACK_ASSIGNMENTS)
     return -1;
 
-  callback_assignment_id_t aid = registered_callback_assignments;
+  if (free_callback_assignment_slots == 0)
+  {
+    callback_assignment_id_t aid = registered_callback_assignments;
 
-  callback_assignments[aid].address = address;
-  callback_assignments[aid].callback_id = id;
-  registered_callback_assignments++;
+    callback_assignments[aid].slot_flags |= SLOT_FLAGS_USED;
+    callback_assignments[aid].address = address;
+    callback_assignments[aid].callback_id = id;
+    registered_callback_assignments++;
+    return aid;
+  }
+  else
+  {
+    // find the free slot
+    for (callback_assignment_id_t aid = 0; aid < registered_callback_assignments; ++aid)
+    {
+      if (callback_assignments[aid].slot_flags & SLOT_FLAGS_USED)
+      {
+        // found a used slot
+        continue;
+      }
+      // and now an empty one
+      callback_assignments[aid].slot_flags |= SLOT_FLAGS_USED;
+      callback_assignments[aid].address = address;
+      callback_assignments[aid].callback_id = id;
 
-  DEBUG_PRINT("Assigned callback id >");
-  DEBUG_PRINT(id);
-  DEBUG_PRINT("/ga[");
-  DEBUG_PRINT(address.ga.area);
-  DEBUG_PRINT("/");
-  DEBUG_PRINT(address.ga.line);
-  DEBUG_PRINT("/");
-  DEBUG_PRINT(address.ga.member);
-  DEBUG_PRINTLN("]");
-
-  return aid;
-}
-
-void ESPKNXIP::callback_delete_assignment(callback_assignment_id_t id)
-{
-  __callback_delete_assignment(id);
+      free_callback_assignment_slots--;
+      return id;
+    }
+  }
 }
 
 void ESPKNXIP::__callback_delete_assignment(callback_assignment_id_t id)
 {
-  if (id >= registered_callback_assignments)
-    return;
+  // TODO this can be optimized if we are deleting the last element
+  //      as then we can decrement registered_callback_assignments
 
-  uint32_t dest_offset = 0;
-  uint32_t src_offset = 0;
-  uint32_t len = 0;
-  if (id == 0)
+  // clear slot and mark it as empty
+  callback_assignments[id].slot_flags = SLOT_FLAGS_EMPTY;
+  callback_assignments[id].address.value = 0;
+  callback_assignments[id].callback_id = 0;
+
+  if (id == registered_callback_assignments - 1)
   {
-    // start of array, so delete first entry
-    src_offset = 1;
-    // registered_ga_callbacks will be 1 in case of only one entry
-    // registered_ga_callbacks will be 2 in case of two entries, etc..
-    // so only copy anything, if there is it at least more then one element
-    len = (registered_callback_assignments - 1);
-  }
-  else if (id == registered_callback_assignments - 1)
-  {
-    // last element, don't do anything, simply decrement counter
+    DEBUG_PRINTLN("last cba deleted");
+    // If this is the last callback, we can delete it by decrementing registered_callbacks.
+    registered_callback_assignments--;
+
+    // However, if the assignment before this slot are also empty, we can decrement even further
+    // First check if this was also the first element
+    if (id == 0)
+    {
+      DEBUG_PRINTLN("really last cba");
+      // If this was the last, then we are done.
+      return;
+    }
+
+    id--;
+    while(true)
+    {
+      DEBUG_PRINT("checking ");
+      DEBUG_PRINTLN((int32_t)id);
+      if ((callback_assignments[id].slot_flags & SLOT_FLAGS_USED) == 0)
+      {
+        DEBUG_PRINTLN("merged free slot");
+        // Slot before is empty
+        free_callback_assignment_slots--;
+        registered_callback_assignments--;
+      }
+      else
+      {
+        DEBUG_PRINTLN("aborted on used slot");
+        // Slot is used, abort
+        return;
+      }
+      id--;
+      if (id == CALLBACK_ASSIGNMENT_ID_MAX)
+      {
+        DEBUG_PRINTLN("abort on wrap");
+        // Wrap around, abort
+        return;
+      }
+    }
   }
   else
   {
-    // somewhere in the middle
-    // need to calc offsets
-
-    // skip all prev elements
-    dest_offset = id; // id is equal to how many element are in front of it
-    src_offset = dest_offset + 1; // start after the current element
-    len = (registered_callback_assignments - 1 - id);
+    DEBUG_PRINTLN("free slot created");
+    // there is now one more free slot
+    free_callback_assignment_slots++;
   }
+}
 
-  if (len > 0)
-  {
-    memmove(callback_assignments + dest_offset, callback_assignments + src_offset, len * sizeof(callback_assignment_t));
-  }
+bool ESPKNXIP::__callback_is_id_valid(callback_id_t id)
+{
+  if (id < registered_callbacks)
+    return true;
 
-  registered_callback_assignments--;
+  if (callbacks[id].slot_flags & SLOT_FLAGS_USED)
+    return true;
+
+  return false;
 }
 
 callback_id_t ESPKNXIP::callback_register(String name, callback_fptr_t cb, void *arg, enable_condition_t cond)
@@ -257,68 +329,108 @@ callback_id_t ESPKNXIP::callback_register(String name, callback_fptr_t cb, void
   if (registered_callbacks >= MAX_CALLBACKS)
     return -1;
 
-  callback_id_t id = registered_callbacks;
-
-  callbacks[id].name = name;
-  callbacks[id].fkt = cb;
-  callbacks[id].cond = cond;
-  callbacks[id].arg = arg;
-  registered_callbacks++;
-
-  DEBUG_PRINT("Registered callback >");
-  DEBUG_PRINT(name);
-  DEBUG_PRINT("< @ ");
-  DEBUG_PRINTLN(id);
-
-  return id;
-}
-
-void ESPKNXIP::callback_delete_register(callback_id_t id)
-{
-  if (id >= registered_callbacks)
-    return;
-
-  uint32_t dest_offset = 0;
-  uint32_t src_offset = 0;
-  uint32_t len = 0;
-  if (id == 0)
+  if (free_callback_slots == 0)
   {
-    // start of array, so delete first entry
-    src_offset = 1;
-    // registered_ga_callbacks will be 1 in case of only one entry
-    // registered_ga_callbacks will be 2 in case of two entries, etc..
-    // so only copy anything, if there is it at least more then one element
-    len = (registered_callbacks - 1);
-  }
-  else if (id == registered_callbacks - 1)
-  {
-    // last element, don't do anything, simply decrement counter
+    callback_id_t id = registered_callbacks;
+
+    callbacks[id].slot_flags |= SLOT_FLAGS_USED;
+    callbacks[id].name = name;
+    callbacks[id].fkt = cb;
+    callbacks[id].cond = cond;
+    callbacks[id].arg = arg;
+    registered_callbacks++;
+    return id;
   }
   else
   {
-    // somewhere in the middle
-    // need to calc offsets
+    // find the free slot
+    for (callback_id_t id = 0; id < registered_callbacks; ++id)
+    {
+      if (callbacks[id].slot_flags & SLOT_FLAGS_USED)
+      {
+        // found a used slot
+        continue;
+      }
+      // and now an empty one
+      callbacks[id].slot_flags |= SLOT_FLAGS_USED;
+      callbacks[id].name = name;
+      callbacks[id].fkt = cb;
+      callbacks[id].cond = cond;
+      callbacks[id].arg = arg;
 
-    // skip all prev elements
-    dest_offset = id; // id is equal to how many element are in front of it
-    src_offset = dest_offset + 1; // start after the current element
-    len = (registered_callbacks - 1 - id);
+      free_callback_slots--;
+      return id;
+    }
   }
-
-  if (len > 0)
-  {
-    memmove(callbacks + dest_offset, callbacks + src_offset, len * sizeof(callback_t));
-  }
-
-  registered_callbacks--;
 }
 
-void ESPKNXIP::callback_assign(callback_id_t id, address_t val)
+void ESPKNXIP::callback_deregister(callback_id_t id)
 {
-  if (id >= registered_callbacks)
+  if (!__callback_is_id_valid(id))
     return;
 
-  __callback_register_assignment(val, id);
+  // clear slot and mark it as empty
+  callbacks[id].slot_flags = SLOT_FLAGS_EMPTY;
+  callbacks[id].fkt = nullptr;
+  callbacks[id].cond = nullptr;
+  callbacks[id].arg = nullptr;
+
+  if (id == registered_callbacks - 1)
+  {
+    // If this is the last callback, we can delete it by decrementing registered_callbacks.
+    registered_callbacks--;
+
+    // However, if the callbacks before this slot are also empty, we can decrement even further
+    // First check if this was also the first element
+    if (id == 0)
+    {
+      // If this was the last, then we are done.
+      return;
+    }
+
+    id--;
+    while(true)
+    {
+      if ((callbacks[id].slot_flags & SLOT_FLAGS_USED) == 0)
+      {
+        // Slot is empty
+        free_callback_slots--;
+        registered_callbacks--;
+      }
+      else
+      {
+        // Slot is used, abort
+        return;
+      }
+      id--;
+      if (id == CALLBACK_ASSIGNMENT_ID_MAX)
+      {
+        // Wrap around, abort
+        return;
+      }
+    }
+  }
+  else
+  {
+    // there is now one more free slot
+    free_callback_slots++;
+  }
+}
+
+callback_assignment_id_t ESPKNXIP::callback_assign(callback_id_t id, address_t val)
+{
+  if (!__callback_is_id_valid(id))
+    return -1;
+
+  return __callback_register_assignment(val, id);
+}
+
+void ESPKNXIP::callback_unassign(callback_assignment_id_t id)
+{
+  if (!__callback_is_id_valid(id))
+    return;
+
+  __callback_delete_assignment(id);
 }
 
 /**
@@ -342,7 +454,7 @@ feedback_id_t ESPKNXIP::feedback_register_int(String name, int32_t *value, enabl
   return id;
 }
 
-feedback_id_t ESPKNXIP::feedback_register_float(String name, float *value, uint8_t precision, enable_condition_t cond)
+feedback_id_t ESPKNXIP::feedback_register_float(String name, float *value, uint8_t precision, char const *prefix, char const *suffix, enable_condition_t cond)
 {
   if (registered_feedbacks >= MAX_FEEDBACKS)
     return -1;
@@ -354,13 +466,15 @@ feedback_id_t ESPKNXIP::feedback_register_float(String name, float *value, uint8
   feedbacks[id].cond = cond;
   feedbacks[id].data = (void *)value;
   feedbacks[id].options.float_options.precision = precision;
+  feedbacks[id].options.float_options.prefix = prefix ? strdup(prefix) : STRING_DEFAULT_EMPTY;
+  feedbacks[id].options.float_options.suffix = suffix ? strdup(suffix) : STRING_DEFAULT_EMPTY;
 
   registered_feedbacks++;
 
   return id;
 }
 
-feedback_id_t ESPKNXIP::feedback_register_bool(String name, bool *value, enable_condition_t cond)
+feedback_id_t ESPKNXIP::feedback_register_bool(String name, bool *value, char const *true_text, char const *false_text, enable_condition_t cond)
 {
   if (registered_feedbacks >= MAX_FEEDBACKS)
     return -1;
@@ -371,13 +485,15 @@ feedback_id_t ESPKNXIP::feedback_register_bool(String name, bool *value, enable_
   feedbacks[id].name = name;
   feedbacks[id].cond = cond;
   feedbacks[id].data = (void *)value;
+  feedbacks[id].options.bool_options.true_text = true_text ? strdup(true_text) : STRING_DEFAULT_TRUE;
+  feedbacks[id].options.bool_options.false_text = false_text ? strdup(false_text) : STRING_DEFAULT_FALSE;
 
   registered_feedbacks++;
 
   return id;
 }
 
-feedback_id_t ESPKNXIP::feedback_register_action(String name, feedback_action_fptr_t value, void *arg, enable_condition_t cond)
+feedback_id_t ESPKNXIP::feedback_register_action(String name, feedback_action_fptr_t value, const char *btn_text, void *arg, enable_condition_t cond)
 {
   if (registered_feedbacks >= MAX_FEEDBACKS)
     return -1;
@@ -389,6 +505,7 @@ feedback_id_t ESPKNXIP::feedback_register_action(String name, feedback_action_fp
   feedbacks[id].cond = cond;
   feedbacks[id].data = (void *)value;
   feedbacks[id].options.action_options.arg = arg;
+  feedbacks[id].options.action_options.btn_text = btn_text ? strdup(btn_text) : STRING_DEFAULT_DO_THIS;
 
   registered_feedbacks++;
 
diff --git a/lib/esp-knx-ip-async-udp/esp-knx-ip.h b/lib/esp-knx-ip-async-udp/esp-knx-ip.h
index 9d9f81db5..86e02c5e8 100644
--- a/lib/esp-knx-ip-async-udp/esp-knx-ip.h
+++ b/lib/esp-knx-ip-async-udp/esp-knx-ip.h
@@ -26,7 +26,7 @@
 
 // Webserver related
 #define USE_BOOTSTRAP             1 // [Default 1] Set to 1 to enable use of bootstrap CSS for nicer webconfig. CSS is loaded from bootstrapcdn.com. Set to 0 to disable
-#define ROOT_PREFIX               "/knx"  // [Default ""] This gets prepended to all webserver paths, default is empty string "". Set this to "/knx" if you want the config to be available on http://<ip>/knx
+#define ROOT_PREFIX               ""  // [Default ""] This gets prepended to all webserver paths, default is empty string "". Set this to "/knx" if you want the config to be available on http://<ip>/knx
 #define DISABLE_EEPROM_BUTTONS    1 // [Default 0] Set to 1 to disable the EEPROM buttons in the web ui.
 #define DISABLE_REBOOT_BUTTON     1 // [Default 0] Set to 1 to disable the reboot button in the web ui.
 #define DISABLE_RESTORE_BUTTON    1 // [Default 0] Set to 1 to disable the "restore defaults" button in the web ui.
@@ -282,6 +282,12 @@ typedef enum __config_flags
   CONFIG_FLAGS_VALUE_SET = 1,
 } config_flags_t;
 
+typedef enum __slot_flags
+{
+  SLOT_FLAGS_EMPTY = 0, // Empty slots have no flags
+  SLOT_FLAGS_USED = 1,
+} slot_flags_t;
+
 typedef struct __message
 {
   knx_command_type_t ct;
@@ -295,13 +301,15 @@ typedef void (*callback_fptr_t)(message_t const &msg, void *arg);
 typedef void (*feedback_action_fptr_t)(void *arg);
 
 typedef uint8_t callback_id_t;
+#define CALLBACK_ID_MAX UINT8_MAX
 typedef uint8_t callback_assignment_id_t;
+#define CALLBACK_ASSIGNMENT_ID_MAX UINT8_MAX
 typedef uint8_t config_id_t;
 typedef uint8_t feedback_id_t;
 
 typedef struct __option_entry
 {
-  char *name;
+  char const *name;
   uint8_t value;
 } option_entry_t;
 
@@ -317,14 +325,29 @@ typedef struct __config
   } data;
 } config_t;
 
+extern char const *string_defaults[];
+#define STRING_DEFAULT_DO_THIS (string_defaults[0])
+#define STRING_DEFAULT_TRUE (string_defaults[1])
+#define STRING_DEFAULT_FALSE (string_defaults[2])
+#define STRING_DEFAULT_EMPTY (string_defaults[3])
+
 typedef struct __feedback_float_options
 {
   uint8_t precision;
+  char const *prefix;
+  char const *suffix;
 } feedback_float_options_t;
 
+typedef struct __feedback_bool_options
+{
+  char const *true_text;
+  char const *false_text;
+} feedback_bool_options_t;
+
 typedef struct __feedback_action_options
 {
-  void * arg;
+  void *arg;
+  char const *btn_text;
 } feedback_action_options_t;
 
 typedef struct __feedback
@@ -334,6 +357,7 @@ typedef struct __feedback
   enable_condition_t cond;
   void *data;
   union {
+    feedback_bool_options_t bool_options;
     feedback_float_options_t float_options;
     feedback_action_options_t action_options;
   } options;
@@ -341,6 +365,7 @@ typedef struct __feedback
 
 typedef struct __callback
 {
+  uint8_t slot_flags;
   callback_fptr_t fkt;
   enable_condition_t cond;
   void *arg;
@@ -349,6 +374,7 @@ typedef struct __callback
 
 typedef struct __callback_assignment
 {
+  uint8_t slot_flags;
   address_t address;
   callback_id_t callback_id;
 } callback_assignment_t;
@@ -358,45 +384,44 @@ class ESPKNXIP {
     ESPKNXIP();
     void load();
     void start();
-    void start(ESP8266WebServer *srv, bool espknxip_webpage = true);
+    void start(ESP8266WebServer *srv);
     void loop();
 
     void save_to_eeprom();
     void restore_from_eeprom();
 
-    callback_id_t callback_register(String name, callback_fptr_t cb, void *arg = nullptr, enable_condition_t cond = nullptr);
-    void          callback_assign(callback_id_t id, address_t val);
+    callback_id_t            callback_register(String name, callback_fptr_t cb, void *arg = nullptr, enable_condition_t cond = nullptr);
+    callback_assignment_id_t callback_assign(callback_id_t id, address_t val);
+    void                     callback_deregister(callback_id_t id);
+    void                     callback_unassign(callback_assignment_id_t id);
 
-    void          callback_delete_register(callback_id_t id);
-    void          callback_delete_assignment(callback_assignment_id_t id);
-
-    void          physical_address_set(address_t const &addr);
-    address_t     physical_address_get();
+    void                     physical_address_set(address_t const &addr);
+    address_t                physical_address_get();
 
     // Configuration functions
-    config_id_t   config_register_string(String name, uint8_t len, String _default, enable_condition_t cond = nullptr);
-    config_id_t   config_register_int(String name, int32_t _default, enable_condition_t cond = nullptr);
-    config_id_t   config_register_bool(String name, bool _default, enable_condition_t cond = nullptr);
-    config_id_t   config_register_options(String name, option_entry_t *options, uint8_t _default, enable_condition_t cond = nullptr);
-    config_id_t   config_register_ga(String name, enable_condition_t cond = nullptr);
+    config_id_t              config_register_string(String name, uint8_t len, String _default, enable_condition_t cond = nullptr);
+    config_id_t              config_register_int(String name, int32_t _default, enable_condition_t cond = nullptr);
+    config_id_t              config_register_bool(String name, bool _default, enable_condition_t cond = nullptr);
+    config_id_t              config_register_options(String name, option_entry_t *options, uint8_t _default, enable_condition_t cond = nullptr);
+    config_id_t              config_register_ga(String name, enable_condition_t cond = nullptr);
 
-    String        config_get_string(config_id_t id);
-    int32_t       config_get_int(config_id_t id);
-    bool          config_get_bool(config_id_t id);
-    uint8_t       config_get_options(config_id_t id);
-    address_t     config_get_ga(config_id_t id);
+    String                   config_get_string(config_id_t id);
+    int32_t                  config_get_int(config_id_t id);
+    bool                     config_get_bool(config_id_t id);
+    uint8_t                  config_get_options(config_id_t id);
+    address_t                config_get_ga(config_id_t id);
 
-    void          config_set_string(config_id_t id, String val);
-    void          config_set_int(config_id_t id, int32_t val);
-    void          config_set_bool(config_id_t, bool val);
-    void          config_set_options(config_id_t id, uint8_t val);
-    void          config_set_ga(config_id_t id, address_t const &val);
+    void                     config_set_string(config_id_t id, String val);
+    void                     config_set_int(config_id_t id, int32_t val);
+    void                     config_set_bool(config_id_t, bool val);
+    void                     config_set_options(config_id_t id, uint8_t val);
+    void                     config_set_ga(config_id_t id, address_t const &val);
 
     // Feedback functions
-    feedback_id_t feedback_register_int(String name, int32_t *value, enable_condition_t cond = nullptr);
-    feedback_id_t feedback_register_float(String name, float *value, uint8_t precision = 2, enable_condition_t cond = nullptr);
-    feedback_id_t feedback_register_bool(String name, bool *value, enable_condition_t cond = nullptr);
-    feedback_id_t feedback_register_action(String name, feedback_action_fptr_t value, void *arg = nullptr, enable_condition_t = nullptr);
+    feedback_id_t            feedback_register_int(String name, int32_t *value, enable_condition_t cond = nullptr);
+    feedback_id_t            feedback_register_float(String name, float *value, uint8_t precision = 2, char const *prefix = nullptr, char const *suffix = nullptr, enable_condition_t cond = nullptr);
+    feedback_id_t            feedback_register_bool(String name, bool *value, char const *true_text = nullptr, char const *false_text = nullptr, enable_condition_t cond = nullptr);
+    feedback_id_t            feedback_register_action(String name, feedback_action_fptr_t value, char const *btn_text = nullptr, void *arg = nullptr, enable_condition_t = nullptr);
 
     // Send functions
     void send(address_t const &receiver, knx_command_type_t ct, uint8_t data_len, uint8_t *data);
@@ -484,7 +509,6 @@ class ESPKNXIP {
 
   private:
     void __start();
-    void __start_espknxip_webpage();
     void __loop_knx(AsyncUDPPacket &packet);
 
     // Webserver functions
@@ -513,6 +537,8 @@ class ESPKNXIP {
     void __config_set_options(config_id_t id, uint8_t val);
     void __config_set_ga(config_id_t id, address_t const &val);
 
+    bool __callback_is_id_valid(callback_id_t id);
+
     callback_assignment_id_t __callback_register_assignment(address_t address, callback_id_t id);
     void __callback_delete_assignment(callback_assignment_id_t id);
 
@@ -521,9 +547,11 @@ class ESPKNXIP {
     AsyncUDP udp;
 
     callback_assignment_id_t registered_callback_assignments;
+    callback_assignment_id_t free_callback_assignment_slots;
     callback_assignment_t callback_assignments[MAX_CALLBACK_ASSIGNMENTS];
 
     callback_id_t registered_callbacks;
+    callback_id_t free_callback_slots;
     callback_t callbacks[MAX_CALLBACKS];
 
     config_id_t registered_configs;
diff --git a/lib/esp-knx-ip-async-udp/keywords.txt b/lib/esp-knx-ip-async-udp/keywords.txt
index 489634883..bc4989bd4 100644
--- a/lib/esp-knx-ip-async-udp/keywords.txt
+++ b/lib/esp-knx-ip-async-udp/keywords.txt
@@ -1,10 +1,13 @@
 # datatypes
 address_t	DATA_TYPE
+message_t	DATA_TYPE
 callback_id_t	DATA_TYPE
 callback_assignment_id_t	DATA_TYPE
+option_entry_t	DATA_TYPE
 config_id_t	DATA_TYPE
 enable_condition_t	DATA_TYPE
 callback_fptr_t	DATA_TYPE
+feedback_action_fptr_t	DATA_TYPE
 knx_command_type_t	DATA_TYPE
 
 # methods
@@ -14,18 +17,25 @@ GA_to_address	KEYWORD2
 PA_to_address	KEYWORD2
 callback_register	KEYWORD2
 callback_assign	KEYWORD2
+callback_deregister	KEYWORD2
+callback_unassign	KEYWORD2
+physical_address_set	KEYWORD2
+physical_address_get	KEYWORD2
 config_register_string	KEYWORD2
 config_register_int	KEYWORD2
-config_register_ga	KEYWORD2
 config_register_bool	KEYWORD2
+config_register_options	KEYWORD2
+config_register_ga	KEYWORD2
 config_get_string	KEYWORD2
 config_get_int	KEYWORD2
-config_get_ga	KEYWORD2
 config_get_bool	KEYWORD2
+config_get_options	KEYWORD2
+config_get_ga	KEYWORD2
 config_set_string	KEYWORD2
 config_set_int	KEYWORD2
-config_set_ga	KEYWORD2
 config_set_bool	KEYWORD2
+config_set_options	KEYWORD2
+config_set_ga	KEYWORD2
 feedback_register_int	KEYWORD2
 feedback_register_float	KEYWORD2
 feedback_register_bool	KEYWORD2