garmin gps?

[BrianG]

The Garmins are nice units. My car-based one will measure at least 118mph. :)

They work of triangulating from several satellites to get position. From multiples samples of position over time, they calculate speed (both average and top), travel times, etc.

Radar requires someone to "shoot" the moving object, while the GPS sits in the vehicle being driven. Just make sure your GPS is VERY securely attached and it isn't exposed if you get into a crash. It would suck to have your new GPS all scratched up!