Lap timer

Mount the phone, press Start before you leave the paddock, and drive. Pitwall finds the track and the line, times every lap, and debriefs the session when you pull in.

Set everything up while the car is parked, and never touch the phone while driving. The timer needs nothing from you on track: it speaks your lap times, and you press Stop in the pits. Keep it on this screen with the screen on: if the phone locks, a call comes in or another app takes over, timing can pause until you return. A short GPS dropout is bridged; a long one ends the lap.