I have the Avic D1 with a backup camera I grabbed off eBay. I don't even realize anymore that I glance at it when backing up.
I was getting ready to back up from a mall parking space .... I see an adult pass my car, I look in the mirrors and out the windows and see nothing and glance at the Avic D1 and see a small kid trailing the adult who had passed me a few seconds ago.
This is not the first time the camera has prevented a possible mishap.
Really, I think SUV's and Minivans (and maybe even pick up trucks) should be required to have back up sensors or cameras when they are manufactured nowadays.