Afrotech Computer Motion Detection So You Don't Have To Go Through The Painful Effort Of Pushing A Key To Bring Your Computer Out Of Suspend Mode
The the other day I picked up a little electronics kit from Radio Shack that let you solder together a motion detector based on ultrasound. Here's what it looked like completed, and with a 12V power supply coming from a pc's molex connector.
Unfortunately there was something wrong with the pcb - solder just wouldn't stick to it properly so in the end I wasn't surprised the thing just didn't work at all. My plan was to mount the ultrasound transmitter/receiver somehere on a wall. Then I would use the circuit to bring my pc out of suspend/screensaver mode as soon as I opened my door walked into the room. I was thinking of hooking it up to the wake-on-lan thingy on a mobo or modifying a keyboard or something. Maybe you'll have more luck.