Homebridge allows you to integrate with smart home devices that do not natively support HomeKit. There are over 2,000 Homebridge plugins supporting thousands of different smart accessories.
Homebridge is a lightweight Node.js server that you can run on your home network that emulates the iOS HomeKit API.
It supports plugins, which are community-contributed modules that provide a basic bridge from HomeKit to various 3rd-party APIs provided by manufacturers of smart home devices.
For more information, see the Homebridge Wiki.