Youtube DIY Zigbee Rain Gauge for Home Assistant (and other applications)

Rain gauges aren't anything new or high-tech, but this video does a great job showing how you can build your own using a 3D printed model, and use a ZigBee sensor to relay this data to Home Assistant. But the concept is so simple, you could easily use a Z-Wave/X10 DS10A door contact, and the concept should work with your favorite home automation application.

More details about the design can be found on his website.