what is the cheapest gps that i can check my mph on my atv with?

 

I though all gps units were capable of measuring mph?

 

garmin etrex
about $115 at Walmart
or online

it's actually a pretty nice unit, waterproof, small
get the ram mount for it and you have a heads up display showing direction/speed, or a map.
or just keep it in your pocket.