Anybody use any for testing?

 

Not a just a phone app but I've heard great things about the Dragy.

www.dragymotorsports.com

 

Yes, doesn't take into account rollout, but you can figure that out once you have a track baseline.

 

The sensors in a phone aren't accurate enough for this kind of thing. I mean, it'll be good to within a second or so, but it's not very useful. Fun to play with for something that's free, but that's it - just a toy. Make sure to hard mount the phone somewhere where it has a good view of the sky.

You need an add-on sensor package - like draggy - for it to be good. Draggy results are proven to be very close to track times. You can also go with a full independent unit like a GTech.