How to display your speed in Google Maps?
It's easy! Just start Maps Speedometer, push your home or back button on your phone, start Google Maps (or Google Navigation) and watch it happen. The app will become visible every time Google Maps (or Google Navigation) is active.
You might want to show your current speed in other apps too. Maps Speedometer allows you to do so: in the home screen, go to 'Applications' and just tick every app you want Maps Speedometer to show up.
If Maps Speedometer overlaps something you need, simply tap the speedometer and it will hide for 10 seconds. Or you can drag the speedometer to another position on your device's screen!
To change your preferences, like units of measurement in mph or km/u, just start Maps Speedometer. Every option is in the home screen. If you do not want the units of measurement to show up, you can choose to hide it. And you can even adjust Maps Speedometer's transparency.
To stop using Maps Speedometer, uncheck the 'Enable overlay' option in the home screen.