I installed a wired system from Rear view Safety on my fifth wheel. I'm very pleased with it. I can park in the storage spot by myself now. I chose the wired version because I heard the wireless systems have some interference when more than about 30Feet. I backed into a tree last fall and while the body shop was fixing the back wall, I asked them to run the wire for me. Then I ran the wire along the frame and up to the hitch. There is a coiled wire connecting the trailer to the truck. I just put the monitor on the dash when I'm towing.
The one I have has audio so I can hear the wife giving directions or kids screaming. It also has infra-red lights to see at night, but I haven't tried it yet.
I might look at the wireless version if I was going to do it again. I think the newer models work better. But I don't have any regrets with the wired version.