[jpk]

Check out a company called "rear view safety" They make a system thats supports up to three cameras. The cameras are powered by a switching unit and controlled by a button on the display.
I have a system on the RV with one camera up high to act as a rear view while driving down the road (it lets me see over the top of the trailer) and another mounted lower to use while hooking up the trailer. I got the display that clips over the rear view mirror, since that's useless anyway.