DIY Virtual Reality Skateboard
This is a really easy project that can be done in about an hour. It is more of a virtual reality experience rather than a game. An accelerometer/gyro goes onto an Arduino board and transmits the angular motion of the board via bluetooth to a (extremely amateur game) I made in Unity for Android phones. This only works for Android phones and your phone must be compatible with Google Cardboard.
[original story: Let's Make Robots]