Most of the Sprinter based manufacturers use a camera that is mounted way up high. Our rig now has two cameras in the back. One is mounted way up hign and is pointed downward to be used as a "back-up" camera. The other is mounted in the license plate and is aimed straight back and can be used as a rear-view camera. The B/U camera shows on our GPS unit in the dash. The rear-view camera shows on a screen in our rear view mirror.
Most of the Sprinter vans with rear view cameras use a larger & cheaper monitor that clips onto the rear view mirror. I think the company that sells them is called "Chinaview".......oops, wrong "Chinavision". Here is a link to the one that I think most of the Sprinter based rigs use: http://www.chinavasion.com/china/wholes ... ch_Display
I don't know how well it would fit on a RT 190, but I liked them when I test drove them.