Genos Garage sells one. I forget what it is called the backup partner or something like that. It gives you a digital readout of distance(in meters) to go after it gets so closs like 10 feet(3 meters) . Also has an audible which can be annoying when the sensor gets dirty. I have one and it works well but in the rain or snow the sensors get dirty and if dirty is more or less worthless but usually a quick wipe will take care of it.