How I use the homebridge-mqtt api and arduinoJson with my esp8266 accessories.
Using a raspberry pi 3, homebridge and homebridge-mqtt to relay commands to raspberry pi zeros and node-red from homekit.
HAP-HodeJS: https://github.com/KhaosT/HAP-NodeJS
Homebridge: https://github.com/nfarina/homebridge
Homebridge-mqtt: https://github.com/cflurin/homebridge-mqtt
Node-Red: https://nodered.org
Mosquitto: https://mosquitto.org
Videos of hardware setup/demo coming soon! - https://www.youtube.com/channel/UCW5E_jmxJpEyn6CLbLvz5hw
Very little configuration required for homebridge, just get mosquitto, homebridge, homebridge-mqtt running on the pi 3.