Huh? Can calculate in this way meh?

To me, benchmarking solely on hp alone is pure crap. In the real world, Power to weight ratio, 0-100 or quarter mile time are the benchmark. Whats the use having a 300 hp with a 2.5 tonne weight, when a sub 1tonne car with half the HP can easily out maneuver and perform better than the big hp car? Not to mention, a low HP car with a high torque makes urban driving much more fun.

Iphone apps are crap. I've tested it and the results were far from actual after dyno. The gyro is not industrial spec tool. They rely on acceleration of the movement (which has a high tolerance) and GPS data (which is also crap AGPS & low frequency) to work out the estimation value. If you drive a 200hp car which weight less than 1 tonne, your HP indication will be higher due to power to weight ratio.