Dynamometer Apps

Has anyone tried a dynamometer application on a smartphone or tablet?  I thought it might be a good idea to find one that actually works, and get familiar with it with the regular car before trying it with the Zed.  Almost anything ought to be better than the "seat-of-the-paints" testing. Some  apps use the accelerometer sensors, some have you drive from zero to 7000 RPM (or the redline) or just start at a crawl and go to about 60MPH or so.

Most of the applications also need inputs like the vehicle weight, driveline losses, frontal area, drag coefficient, etc., and a mount that is strong and vibration-free.

If they really work and provide reasonable results, then it would be worth the savings in dynamometer rental fees to  find a deserted road for testing somewhere.