Our apartment's Nest thermostat is located in a hallway which never seems to be the same temperature as the rest of the house. Since until recently, Nest didn't have remote sensors, I decided to build a few myself. Each sensor reports to my Smart Things hub, which can override the Nest and heat or cool the house.
Designed using an ESP8266 wifi module.
Boards was successfully fabricated using OSH Park which I highly recommend to anyone interested in creating prototype boards.