An ongoing list of resources for developing Apple Homekit stuff
- Homekit Developer Documentation
- Homekit Accessory Protocol - noncommercial version; required Apple Dev account to access. If you want the commercial verson, you have to join the Apple MFi program.
- Apple Homekit ADK - Apple's official open source ADK for Homekit
- HAP-NodeJS - Node.js implementation for Homekit Accessory
- Homebridge - Node.js server for Homekit
- ESP Apple Homekit ADK - Espressif's official port of the Apple Homekit ADK for ESP32 and ESP32-S2
- ESP Homekit SDK - Espressif's homegrown SDK for Homekit dev hversus the ADK port above)
- ESP-Homekit - Homekit implementation for ESP-OPEN-RTOS
- Arduino-Homekit-ESP - ESP8266 Homekit implementation for Arduino.
- HomeSpan - ESP32 Homekit implementation for Arduino. Documentation is excellent; this is a good implementation to look at if you're looking for an understandable reference implementation of HAP R2.
- nRF Connect SDK - has a Homekit add-on for nRF52, nRF53, and nRF91 devices (support both Bluetooth and Thread!)