[onewhippedpuppy]

From what I've heard, the cheapo kits with a dedicated monitor aren't very good, which would be the only removable option. Never seen a magnetic camera either, I would think it would be prone to moving out of adjustment. There are some pretty good retrofit kits on Ebay that have the display in the rear view mirror and the camera somewhere subtle, like the rear badge. You could also upgrade to a double DIN head unit, most of which offer a rear view camera option. What kind of truck?

My 2012 F150 has the display in the rear view mirror and the camera in the Ford oval badge on the tailgate, it's the OEM camera. Once you have one you'll wonder how you lived without it. You can also impress people by backing your hitch ball perfectly under your trailer hitch in one shot, it's funny as hell when they don't know you have a camera.