I have replaced Chinese made brains of air-source heat pump with my own microcontroller that makes whole system much more efficient even at very cold winter climate. It provides heating to water circulation system inside the house. All hardware and software parts are made open-source.
Robot that sitting in a pot with a plant and watches if somebody is around. If you are in near proximity it will communicate plants needs to you.
Ping pong game made as a proof of concept using active infrared LED markers, Leap Motion and Oculus Rift DK2