None of the speedometer apps are working on my iPhone 5s
I really want to use my phone as a speedometer but whatever app I try doesn't work.
iPhone 5s, iOS 9.3.1
Is your phone working ok otherwise?
Try a Forced Restart. Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears. You will not lose anything. Then try reinstalling one of the apps.
If still not successful I would contact the app manufacturer. Check for a contact link or email on the app itself.