More than 300 different modules(adapters) that can be interconnected with each other. E.g. Homematic or KNX can control HUE or sonos and vice versa.
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Google Home - Set up, manage, and control your Chromecast, Chromecast Audio and Google Home devices.
Domoticz - Domoticz is a lightweight Home Automation System
Jeedom - Jeedom is a complete home-automation software.
Android Things - Build connected devices for a wide variety of consumer, retail, and industrial applications.