I'm planning to use my Pi in a Chameleon Suit. I won't go into too many details, but it will include a colour sensor, camera and a large array of RGB LEDs, all interfaced together and driven by the Pi. The RGB LEDs will form a large dot-matrix display which will be able to be modified in real time.
The suit will cover my entire body and I'll be able to hide in plain sight against brick walls, etc.