I am considering changing my Sony head unit for one of these. In the item description it mentions automatic switching for a rear view camera.
http://m.lightinthebox.com/8-inch-1...gps-canbus-rds-wifi-ipod-fm-swc_p2070076.html
http://youtu.be/Fv4iA2V8e0w
I have a similar aftermarket unit. The unit is great, it's loaded with features, bluetooth navigation, backup cam, dashcam w/dvr, sd card playback, ipod interface, etc. It's basically plug and play, but you do have to buy the camera and wire it yourself, and route and mount the gps antenna.
The android based software is somewhat unreliable. It crashes occasionally and has problems with navigation freezing up. Each software update made some things better and other things worse. I found a forum thread that showed me how to revert it to the older WinCE based software and it works great.
If you're going to buy one of those I highly recommend looking for a S100 model. It comes stock with the WinCE software and if you're really dying to try out the Android on it it can be upgraded. There are about 5 different manufacturers using the same faceplate covering different head units, so make sure it says it's an S100.