Not trying to hijack, but I connected this strobe from Custom LED. Wired in parallel with my rear brake light and it works whenever I apply the front or rear brakes because of the CanBus. Very simple installation. It has three wires, red, black and white. Red and black wired into the brake light circuit and white is used to program one of seven different flashing patterns (I went with the hyper-spastic quick flash).
I have had many positive comments about it and it easily mounts below the license plate on the stock GS tail. They have multiple colors but I chose red to accent the brake light.
Check it out here