I turn it on separately. It is a little bit easier to wire it up that way. But I have found that there are times when you are going forward but want to see what is happening behind. If the camper is packed to the point the rear view mirror is blocked the camera can help some.
I did try the wireless setup but too much interference and inconsistent picture. So I went hard wire. Not fun drilling a hole in the cab of 2 week old truck.
Yeah, I know the feeling. I installed a 120v outlet in my cab shortly after getting the new truck. It was hard to chew a hole the brand new center console but I'm glad I did. That outlet comes in handy to run the computer and the occasional tool. I'm going to modify the camper in back so I can access the outlet in the bed too.
I like the ability to turn the camera on anytime- good job.