Originally Posted by ax0n
GPS? Hopefully you mean satellite transponder (like LoJack, satellite phones, and OnStar use). GPS will only recieve orbit data and time information from satellites (it then calculates its location based on those signals, and puts you on a nifty map)
Yup!
For additional security against "grab it and go!" theives (the variety that will steal a bike locked to itself through the wheels and frame) a cheap, ultrasonic transducer-based proximity delta sensor could send a once-per-second pulse to an inductor coil whenever it sensed something getting closer to it. This would add a painful (but not lethal) high-voltage, low current bite to the bike's frame, to make holding onto the bike a "shocking" experience. This would be able to be armed, disarmed, or "actively pulsing" regardless of sensor -- remotely and independently of the bike locking system.
Good idea - but the handlebars and seat are pretty nonconductive.
Someone my friend knew rigged his Expedition to shock the driver through the steering wheel if he didn't flip a switch beneath the dashboard. One day he was on a date and forgot about the switch. Woke up in the hospital without the skin on his palms. A few years later he killed someone and buried them near campus (Hofstra). Had a few screws not tightened enough...