Speedie
Check your speed in miles per hour, kilometers per hour, meters per second and knots.
Speedie uses the GPS to work out which direction you're heading in. This means it works when your iPhone is upside down!
Keep track of your speed from your wrist.
Swipe down from the top of your iPhone to see your current speed.
Note: Speedie requires GPS to get your speed and direction. It may not work indoors, in tunnels, or around tall buildings.
Also note that Speedie contains no creepiness. It's not free (it costs about a dollar) but there are no ads, there's no third-party crash reporting, and not even any analytics. You're trusting this app with your location data, so it's very intentionally not doing anything creepy with it.