I just ordered this today.

http://www.overstock.com/cgi-bin/d2.cgi?PAGE=PROFRAME&PROD_ID=21092#

I will update the progress and evaluation score

I'm interested on the ease of the install and how well it works. I am planning to put one on my wife's minivan at some point. They sell a lot of them on ebay too.

I know you can get proximity sensors that would work for a backup sensor application from a lot of places like digi-key or even radioshaq. I've thought building a backap alarm for my wife's car I just haven't taken the time to design it out yet.

I tried to install the backup sensor today. No luck. I think I got a bad one. It doesn't have any power at all. I called the vendor to get a replacement.