Most aftermarket backup cams have a small pigtail at both ends of the video cable. About 8 inch long red pigtail. This pigtail can be used to send power from the head unit back to the camera or can be used to tie into the reverse light at the back of the car and then the end near the head unit is tied into the reverse trigger wire of the aftermarket stereo so that it switches to the cam automatically.

 

That makes sense. My experience is with a wireless camera (which I would not recommend due to lag time).

 

Agreed. I tried out a wireless cam with a small display one time before swapping over to wired. It was a grainy picture, tiny screen, poor quality screen, kind of low res, and laggy for sure. Wired is better. This was a number of years ago on my 05 Tundra DC so there may be much better wireless cams these days that don't have as much lag.