Simon Bisson wrote a cool story for ZDNet. It involves using an open source tool called Homebridge that can be used to integrate smart home devices that don’t natively support HomeKit.
The plugin ecosystem is where Homebridge really excels. By having its own defined APIs, it’s possible for anyone with access to developer documentation to build a simple translation layer that links devices to HomeKit and to Home (and to Siri). Most of the plugins are on GitHub, so if you want additional features or support for alternative hardware, you can fork existing code and start to add your own features.
Check It Out: Using Open Source Software to Extend Apple’s HomeKit