Oh, try searching an app called AA GPS HUD on Android. It does speed to the tenth of a mile and you can throw on your dash and it will project as heads up display. Kinda hard to see sometimes though so I always just let it rest in the steering hub of the wheel. On IPhone I can't help with an app.
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When I was a child, I used to talk as a child, think as a child, reason as a child; when I became a man, I put aside childish things.
1 Corinthians Chapter 13 - 11