I just downloaded this app and its pretty cool. For those who dont know, it tests acceleration, g force and HP in several different ways and then it gives you a graph, and all of the info.
Heres 2 runs from the Miata. Pretty slow, but it was my 1st and 2nd try.
On the first run, I didnt realize you needed to calibrate the device which is why the 2nd run graph is a bit smoother. I think its pretty cool, but it does cost $12.99. Apparently several magazines have tested it against their own devices and it holds its own.
There's free ones out there that do, pretty much, the same thing. I have the BMW M version of it and it seems to work decently well. I think my issue is I have no where to mount my phone.
I looked into the BMW one the reviews are not very good. I have read about dynolicious in several magazines, and read a lot of reviews and its very accurate regardless of if you can get a sub 3 sec 1/4 mile time sitting on the couch or not.
I have pocket dyno. So long as you're not using it to get accurate horsepower readings it's pretty accurate. I ticked off a 0-60 of 5.9 seconds with front wheel drive only in the R. (Infamous angle gear failure.) Haven't done a run since I got the car back from the shop.