Originally Posted by
msu2001la
The OP is describing a LoJack. They need battery power, but theoretically someone could rig something up for a bicycle. I know LoJack makes products for motorcycles, so they've probably got something fairly compact.
I just did a quick search - there are a number of products shipping or in development, some more discreet than others. One is intended to be hidden in the bar end, another in the steerer. Could be interesting.