This is the odd one out here, as the Supa didn't 'detect' anything as it's a camera and screen system. The display was part of a large rear view mirror which fitted over the original, and came on when reverse gear was selected. A camerawas mounted in the bumper and gave an excellent picture. Downsides were that auto-dimming mirrors would be rendered useless, and the wide angle lens could make it difficult to correctly judge a distance.