Add a OEM camera to back of travel trailer and wire to head unit

I got an idea I'd like to kick around, or get shot down on... (That usually happens to me here....) I need to add a camera to the back of my travel trailer and actually use the 4runner head unit to view it seamlessly. I already installed the front camera kit "any time rear/front camera kit" from Caliraised with front camera and relay and switch and it works perfectly. Just got off the phone with "Anytime backup camera" site guy at https://www.anytimebackupcamera.com/ who puts that kit together (caliraised is just a dealer) and kicked this idea around with him... I'd need to buy from him probably a camera, 2 extension wires to extend the camera's length of wire all the way to the back bumper of the 4runner (along with a connection I'd have to add in at the bumper when towing the trailer), and a relay that does the switching, and a simple single pole- single throw switch. It all adds up $$$ but I'm thinking of doing that and be able to view my existing rear bumper 4runner camera and switch when towing to the trailer camera all on my head unit. Film at 11...

Mind you, I'm doing this all to avoid an additional screen to clutter up my dash area. I already bought the Yakry backup camera and screen and it worked great, until it didn't... And I need the room up front for a phone mount and ipad mount for GPS maps.

Nemo

 

Genuinely curious as to why you need a back-up camera on the rear of a trailer. When backing a trailer, and I do know a thing or two about this (Class A CDL), all you need are your mirrors. I don't see how a camera will help you, unless you're backing into a spot and you want to get close to a wall or something similar without a spotter. Guess I need a little more info...

 

I need it to see that darn little car or motorcycle that's disappeared from my mirror view, wanna make sure I don't ignore him as I change lanes and get surprised, also for backing up into s small space like my side yard where I store the trailer, as you mentioned.