I installed a backup camera on my Magnum. It displays on the REC NAV receiver when reverse is used. It was modded with the "TV and Nav 2 Go" video input. I might add one to my Caliber's REV NAV unit. It will also display the Magnum DVD player.
I test drove a Nissan Murano this past weekend, and they had the reverse camera. It was kind of cool. But it would take some getting used too because the image is bowed like your looking through a peep hole. lol!
my buddy installs them all the time. primarily on big trucks. theres no point in having a mod like this on a caliber. i recommend doing the backup sensors if anything. 4-6 different sensors installed on the rear bumper that will make make beeping noises as you get close to something backing up. as you get closer the noise gets faster. thats what id do.