for $13 it was worth it. the 0-60 and 1/4 mile times are supposed to be very accurate. To get good HP numbers, you have to know an accurate weight for your car, and you have to run a 1/4 mile as fast as you can. I haven't had the chance to do that yet (weak clutch). I'm looking forward to trying it to see the difference between mods.
Oh - and you have to make sure the iPhone is held securely or the numbers go wonky.