Create an android app that alerts user when he reaches speed limit while driving!

I would like to create an android app that uses the phone's GPS to detect the user speed while driving and compare it with the street speed limit data from (Open Street Maps, HERE maps, or TomTom maps) API and then send alert the user with a sound that he is reaching the speed limit. I want the App to work by itself in the background while the screen is off and make a sound when the user drives faster than speed limit.
Example App (Velociraptor) can be found on Google Play store
Here is the link to the app:
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