[greglepore]

I had a wireless system and it failed 2x. After the last time, I put a 4 input video switchbox under the dash. I have 3 cams currently, one on bumper for backing, one on bed front to see gooseneck hitch, and one inside the trailer to keep an eye on horses in transit. My headunit allows me to turn on monitor without reverse light wire being tripped, but you need constant 12v to camera for that (only one currently wired is the inside trailer one-with a kill switch for storage).

I'm temped to put a 4th (wired) on back of trailer, not so much for steering guidance as for safety as you can back into/over something that is otherwise hidden (ie a dog). I would do it wired.
I ran a video extension cable to rear bumper of truck and used a rca union (just a thing with two female ends) to join to another extension cable from the camera. Would need a 2nd cable for a trailer rear cam.