Share 'A back-up camera'

Has anyone added a back-up camera to their smart? A stand-alone unit, not one that's part of an A/V system. I want to add one to my wife's new cabriolet because rear visibility is severely compromised compared to my coupe (which isn't the best anyway). The unit I have came with generic instructions but it sure would be nice to hear from someone who's done it before and "cracked the code" for a…