07 tahoe rear view camera

You can't. The factory nav gets it commands directly from the trucks BCM. It not only knows when it's in gear, but when you are moving, stopping these functions. As for the camera, i don't believe that's pssible either. The camera command to turn on is set with a Tech2 computer. Just to let the truck know it's even there we have to load the data from the truck to the Tech2, then connect the Tech2 to an online PC at the dealership. Online at GM's own website the functions are changed for camera, then loaded back to the Tech2, which is then loaded back to the truck. GM does it this way to keep track of changes made to the BCM. I've done this many times and there is no setting at GM online services to change anything camera related other than simply on or off.