SpeedX10 is a speedometer with several functions.
Press start and the app is running.
In addition to speed you can read your Latitude, Longitude and Altitude.
More functions are:
Time from start, average speed, trip distance, bird distance from start, total distance since reset (odometer) and heading.
Also magnetic heading (compass) and calculated average GPS course from start and GPS course for return.
You may choose between km, nautical miles and statue miles.