Tired of doing the mundane task of opening your door? This hack from Sieuwe Elferink takes care of that for you, using an Arduino Uno for control.

When someone comes within 50 cm of an ultrasonic sensor attached to the door, the Arduino uses an H-bridge relay to power a windshield wiper motor, which opens and closes it via a linkage setup. Another sensor is implemented on the opposite side of the door, allowing hands-free travel both ways!

Want to build your own? You can find instructions here, while code is available on GitHub.