I have a wireless camera that I installed over the fuel fill door to help line the coach up at the fuel pump.
They are really far from being wireless. The only wire eliminated is the wire going from the camera to the monitor. You have to provide 12 volts to the camera and maybe locate the camera antenna so that the signal can be received by the monitor. Used as a rear view camera, the 12 volts is sometimes taken from the wires going to your back-up lights. If you do not tap in to your back up lights, and you want to watch the toad as you are going down the road, than you need to find a wire that has 12 volts whenever the ignition key is turned on. Not easy on the rear of the coach.
Then you have to supply 12 volts to the monitor that comes on with the ignition or back up lights.
In any case, the installation is not as simple as they make it sound.
I was fortunate because my camera connects with a bluetooth signal through my GPS screen and I can turn it on and off with the touch of a button.