The 2 backup cameras that I've installed had a signal wire built into the A/V cable, I spliced it into the positive line on the rear backup light on the one side and the head unit on the other side. works like a charm and less intrusive than trying to find the right wire up on the steering column. the head unit and backup cam are pretty high on my list of things for next year, and I might look at patching into the towing wiring harness because of the camera design i'll have to use, the 2 that i did replaced the license plate light and all the wiring was neatly tucked away inside the trunk of the cars ('12 WRX/'14 elantra)