I have a caliper activated brake light on my bike. I wil take a short vid for you. It uses two "AA" batteries. There is a satellite switch on the handle bars that turns on the "parking light" at night and the turnsignals.
I do not remember the company that makes it. It is all L.E.D.
http://www.angelfire.com/ny/ianjiggyroom/brakelight.mpg
Dial up do not even try it!