Great app. Heres how to use it.

I managed to figure out how to use the app in 5 minutes of playing with it. Easy instructions:

Calibration happens automatically. If you want you can force it to calibrate manually by hitting the wrench in the "Acceleration" page, but its generally unnecessary.

To get automatic lap timing working:
1) Create your car and track at some point by hitting the wrench in the "Classic" or "Racers" page. Select your car/track.
2) When you get to the starting grid for the first time on that track, hit the "More" page, then "POI List", then "+". This sets your current location as the start/finish line.
3) Hit Go on the "Classic" or "Racers" page and start lapping!

4 stars only because Harry should be writing these instructions and not me. This app has far more features than any of the other track day apps out there; theyre just harder to get to.

lapped_u about Harry's LapTimer Rookie