[Madmanmoe64] has really done a fantastic job with this burglar alarm built into a zippo. He crammed a picaxe microcontroller, some IR LEDs, an IR sensor, a battery and various switches in there quite well. It almost closes perfectly, something we think he could remedy if it really bugged him that much.
It has several modes, all initiated by a different sequence of button presses. There is the proximity alarm, which sounds when something moves very close. The reverse proximity alarm which sounds when you remove something from its immediate vicinity. A doorbell mode, and a silent alarm mode. Check out the video after the break to see it in action.