Here's a copy of a reply to someone else that i posted last month.
I have a factory-installed Camos video camera on the rear of my trailer. Here's a picture of the system.
I recommend that you install it the camera up high rather than on the bumper so you can see more. These cameras have such wide angles that you will be able to see the horizon down nearly to your rear bumper, making it easy to see how far you are from any obstacles when backing. When driving, you'll be able to see over the vehicle immediately behind you and get a better feel for traffic. I also use mine to keep an eye on the motorcycles on my Hydralift.
The camera doesn't look like much. It's white and blends in with the trailer gelcoat. Most people never notice it. I don't think anyone would think of taking it. The video cable runs through the insulation in the rear cap and then forward with a wiring bundle into the generator compartment in front where it connects to a transmitter. But frankly the transmitter is strong enough to shoot all the way through the trailer into my truck cab with no problem. I tried it.
Make sure you install a power switch for the camera and transmitter so it doesn't draw down your battery when you're camped. Expect to pay about $700.