Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Metastream - Watch streaming media with friends
ioBroker - flexible and modular application for the IoT and Smarthome
Watch2Gether - Watch2Gether is an app that allows multiple people to watch the same content simultaneously and interact with each other while watching.
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
StreamParty - StreamParty is a watch communiry, that allows you to watch video streams in sync with the people you care about, on multiple services.