I installed the Visipath modulator on my BV500 last year as well as a brake flasher purchased from here:
http://www.comagination.com/modBike.htm
The headlight modulator was a simple plugin unit that sits between the bulb and existing socket. I ran the light sensor wire out the side and secured it to a brake line with a cable tie. It sticks out about 1/4 inch past the edge of the side of the handlebar cover.
The brake flasher required splicing a couple of wires, but everything fit inside the back of the tail light housing without a problem.
The only hard part was parts removal and replacement in order to get access to the headlight bulb.