Unlike most speedometer apps, there’s no kitschy dial, Proton just gives you the facts. Current, top, and average speeds, presented in large, bold, numbers. Customizable with different colors and measurement types, from MPH to knots.
And with the premium version, Proton will show you a graph of your speed over time, and allow you to export all the logged speed and mileage data in a convenient CSV format.
More information, feature list, and screenshots: http://protonapp.com/
Full Version - $1.99