Home Assistant is the best open source project idea of this decade. It provides a solution to two niches:
* It connects smart home components that otherwise can't be connected.
* It offers you to connect over 1000 components by simply configuring a few variables.
It runs on low power devices (such as Raspberry Pi), its core and its components are all created using people's favorite scripting language (Python), and it is constantly being improved by a thriving open source community.