just completed my first hardware project for my OpenHAB setup: A simple and cheap wifi sensor for temperature and humidity. This is how the sensor data looks in the classic UI:
Look for “Temperatur” and “Luftfeuchtigkeit” - my interface language is German. The sensor is based on the cheap ESP8266 wifi microcontroller and a DHT22 temperature/humidity sensor. It looks like this:
The PCB is around 5x5cm and can be built in 30 minutes from scratch. If you want to know more, the complete project description (including code & schematic) is on github:
The README also contains the item definitions etc. for integrating the sensor into OpenHAB.