Back up cameras are getting smaller and better. Our fleet, mostly Fords, were upfitted after purchase. Seems Ford has caught up to the market and the cameras are almost standard equipment. The models we used to install were HitchCams. In the beginning, they were small cameras with a 5" screen on the dash. After a while, they went to a 3" or so screen on the dash. All versions worked great! Still do. These days, the camera is in the rear view mirror. Here is the earlier version we used to buy:
http://www.topshop-mn.com/reverse-sensor-systems Seems like they are harder to get now that OEM already has them upfitted.
The wiring is from front to rear with a weather proof connection at both ends. I believe the longest cable you could buy was something like 60', which works great for trailers and such! Simple connection at the power source, usually under the dash. A signal from the reverse circuit actuates the camera.
