RV Backup cameras also allow you to see what's behind you while driving down the road. Halo brand has side marker replacement cameras, so they also cover the blindspots. Whatever you do, please stay away from Tadi Brothers "kits". I had a bad experience with them.
I ended up for the TT buying a cheap camera and monitor from Amazon. It worked fine. For the 5er, I will likely end up with two cameras on the back, one being Ford user place, and probably Halo. I don't believe Ford allows the camera to be on full time while driving down the road.