I heard about it on the radio yesterday.
"Trapster is a social networking mobile application and website, provided for free, that maps out and alerts users in real time to the presence of live police speed traps, red light cameras, speed cameras, and areas where police often hide. In addition, it allows users to record trip data and share it via the web, including interfaces with Facebook and Twitter. Trapster was recognized by Time Magazine as one the 10 Best iPhone Apps for Dads in June of 2009, and as one of the 20 Sexist Apps for Men by iSmashPhone.com in July of 2009. In addition, Wired listed Trapster as the number 1 application in their 10 Mobile Applications that Make the Most of Location and CNET named Trapster as their number 1 free iPhone automotive app.