This app was mentioned in 2 comments, with an average of 2.00 upvotes
It is a movable sizable floating timer. You can customize the length. So when I arrive, I tap it and it starts counting down. I give an extra 30 seconds to make sure I get credit before canceling. You can even have it auto text a message to your pax when you start it.
https://play.google.com/store/apps/details?id=com.floatingtimerapp
Professionals don't need pocketwatches on chains, we got apps!
https://play.google.com/store/apps/details?id=com.floatingtimerapp&hl=en
THE RIDESHARE GUY lists Rideshare Timer as one of the "12 Must-Have Apps For Rideshare Drivers"!!