I have been waiting for cool projects using the TI EZ-430 wireless watch, and it comes up one today! You can unlock the door wirelessly by just taping the watch screen with a sequence. The sequence is then detected by the internal accelerometer and translated to a door lock pattern. If it is correct, it would unlock the door:)
Hard to say how cool is it, Lets see the demo! Cool Project, Ziyan!
Details of implementation: https://ziyan.info/2010/01/secure-wireless-door-lock/