The community driven project has already created plugins for a bunch of different HA controllers to make the home build sensors work seamlessly with other propriety products.
The step-by-step guides will get you up and running quickly to detect motion, distance, temperature, humidity. The site also provide actuator examples for controlling lights with relays or blinds using a servos.
Sensor building blocks can be purchased everywhere and consists of Arduinos, NRF24L01+ transceivers from Nordic Semiconductors and an open source communication library."
Link to Original Source