motion sensor [2/15/09]

It seems the standard, cheap, motion sensor on the market is the PIR from Parallax. It detects motion up to 20 feet away using infrared-sensitive elements to detect changing patterns of passive infrared emitted by the objects around it. There's lots of source code from Arduino floating around relating to this sensor, mostly one that turns a light on and off. I think these sensors could work for the final project, placed behind the mirror. If nothing else it might be a good place to start experimenting.