reverse distance sensors

JC Whitney has a pretty cheap one for about $40. Part number is ZX529036B. Has two sensors. Dont know if it is good enough for what you want.

I found a number of them on a previous net search.

I believe we call them obstacle detection or object detection. Maybe you can get better search hits with that term.

Just do a google search on backup sensors.

I have a talking backup sensor with three sensors on my Odyssey and it works great..

I have a similar set up in my T&C, and it is pretty worthless. It stops giving you distance readings when you get to a foot or less. I can easily do a visual estimate to within a foot. I need the help when I am getting under a foot. I would rather have a camera back there.

------------- Alex

You could duct-tape a squeeze-bulb bicycle horn to a piece of 2x4 duct-taped to the back bumper- hear the beep, you're there.

Dave

You know, Honey, you could just install some kind of bump on the pavement, exactly at the spot where you want your wheels to be. Then back up slowly until you feel the rear wheels hit that bump!

Someone could move it back on you as a practical joke, while you're gone, so you hit the wall first. For that, you need a bump-move sensor with a wireless transmitter. When you are within range of the bump, the receiver device can pick up the signal from the bump which tells it that it has been moved! That can be turned into a voice warning: "warning: bump has been moved! Vehicle may contact wall!" And of course, if no signal is received: "Warning, bump malfunctioning, stolen, or bump battery low. Vehicle may contact wall!"

I've also seen trucks and vans with foam padding taped to the rear bumper. The idea there must be to keep backing up until you hit the actual wall.