SpeedLimiterPro is your new assistant to stay within the speed limit.
It displays your current speed and automatically compares it to the local speed limit. As you approach and then exceed the speed limit, the app will alert you using audio. You can set the tolerance value you want between the speed limit and the alert. You can also choose if you prefer KM/H or MPH.
Disclaimer: Continued use of GPS running in the background can dramatically decrease battery life.