Solar Power Monitoring, well that and most of the other energy consumption in a typical house. Mostly I was interested in how my 1900 Watts of solar panels was working.
Outdoor Environmental Quality station. Arduino + Esp8266 + Dht22 + Bmp180 + Light Meter
Temperature, Humidity and Pressure using a ESP8266 and a BME280
Temperature, Humidity, Pressure, Motion Detection and Light Level in our F5 home.