I like the idea of Trapster or some other functional similar well-designed app.
Though I have been experiencing issues running Trapster (in New South Wales, Australia, usually a few hours north of Sydney) on my Samsung Galaxy S GT-I9000 running Android 2.2 Froyo.DTJP5.
Using the older ver. of Trapster (from early Dec 2010) it seemed to work OK for the couple of trips I did, however after updating it to this newer ver. it rarely completely loads and pretty much freezes whilst apparently loading/generating the map & my location. Will research it more and try a few things to see if I can improve it.