I also installed a backup camera about a month ago. It takes about 2 seconds for the Nav screen to display and it does give a good field of view and image. However, with your eyes already going all over the place backing out, I felt that the audible sensor would give an added edge of safety. For me, it's a 'must have' as I also installed one when I got my 2001 Sienna. These things should be standard equipment in all cars, and probably will be some day. Having it operational for only a day, it starts to beep, beep, beep, at about 5 feet from an object. It gets more frequent as you get closer to the object until it is just a steady beep. There is also indicator lights that flash yellow then a steady red. On my Sienna, it is a voice: 'Five Feet' 'Three Feet' 'Warning 1 Foot' then a steady beep.