Hey Mathew, not sure how much work you want to put into this project, but I really like the Voyager stuff from RV Cams, I have instaled the same system on three of the coaches I've had they have a really nice 7" colour monitor that has imputs for four cameras as well as a GPS system I've always installed their colour ,tilting camera at the rear, and on my latest unit, I added the side cameras as well , which are actually really cool. The hardest part of the install is running the cable for the rear camera, as it won't work with the existing coax. The stuff is a little pricey , but if you talk to Tim down there( the owner) they seem to discount the crap out of everything if you are ordering a whole system. They are super nice people to deal with, check out their website
Dave