This is a lightweight app designed as a backup or means to validate your current speed. This app is free, will always be free and has no ads to clutter the screen. It will display your speed in either miles per hour or kilometers per hour.
If you are unsure of the speedometer in the vehicle you are using, you can now check it with this app. If the vehicle you are in doesn't have a speedometer, you can check it with this app. If you have made modifications to your vehicle that would effect the speedometer, you can check it with this app.