[iPhone God App] It was found using the Speed 3The GPS Speedometer actually

Speed 3 is a drop-dead simple speedometer for iOS that uses the location data from the GPS to provide a near-accurate representation of how fast you're actually traveling.

Featuring lush graphics and a clear, legible display. Speed has an inbuilt compass and odometer/tripmeter. With support for miles, kilometers and knots, Speed is the perfect road, sea or air speedometer.

Simply swipe the screen upwards to reveal the settings pane.

NOTE:
As this works using the GPS, you will have to be moving at a certain minimum speed for it to register - walking or running generally won't work. An iPhone or iPad WiFi+3G or WiFi+4G with a GPS is required for this app. It will not work with a WiFi-only iPad. If you see the flashing GPS indicator, you do not have a GPS lock.

Continued use of GPS running in the background can dramatically decrease battery life.

STUCK AT 0.0?
Verify that you have allowed location services for Speed in the Settings application. Also make sure you have good GPS coverage!