Not accurate
I tried it out at Heartland Park Topeka on a motorcycle track day. I started the lap timer and put it in my jacket pocket and the laps were about 15 seconds slower than what I was running. I compared my laptimes to my garmin virb. Maybe your not supposed to put your phone in your jacket pocket but I am not comfortable attaching my phone anywhere to my bike. Maybe a ram mount might be more accurate or maybe in a car, not sure but it was not accurate for me.