I have used a program called digihud forever.I do, and I know you can use GPS but I've never looked into it.
it also hasn't changed in forever.
it's super basic. open it up, displays compass and speed.
automatically records top speed.
no ads, no data useage, nothing.
DigiHUD Speedometer - Apps on Google Play
GPS digital speedometer with head-up display (HUD) for phone or tablet.
play.google.com