Poor Man's Do It Yourself Security System
Some guy designed a system to take a picture with a cameraphone and send it back to you whenever you text it from another phone.
Utilizing a couple of cameraphones, a microcontroller, solenoid relays, a photoresistor, wires galore, a soldering iron and a robust picture messaging plan, this cameraphone activated cameraphone can be used to snap pictures of a pre-defined location whenever you get curious.
I'll admit the system is fun to watch in action, but come on. Video camera systems aren't that expensive. Plus they have the added benefit of, you know, not looking like a freaking bomb.
Video of the device in action after the explosion.