OP stated he wanted a rear-view camera, not a backup camera. Different purposes.
I put a wired rear-view on my trailer, so I can see the narrow cars that get too close, and are not visible in the side mirrors. I like to know if there is someone there if I have to hit the brakes hard in nasty traffic. I leave extra space in front of me if I know I can't stop as fast, so I don't get rear-ended.
I looked at wireless, but techs told me they get too much interference. So, I got the wired kind, got an extra cable, and ran it myself, both on the trailer, and on my TV. simple to do, and completed in about an hour. Not worth paying someone more than $100 to do, if you just don't have the time or inclination.