I used sirmorris's method to store data on an sd card:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1235125412
It's an arduino set up. I use it on a motorcycle to count and store pulses from the speed sensor. With the count(pulses/second) stored on the sd card, the card can be removed from the arduino cktry., then plugged into my computer.
The data can then be loaded onto a spreadsheet, such as excel, then the data can be used to calculate things that happened over a period of time, speed, acceleration, rpm, make curves on the spreadsheet, calculate derivatives or integrals from the various curves.
I haven't been able to calculate torque or hp yet, but I can graph speed and acceleration curves. If I make any mechanical changes to the bike, those curves will give an indication of any changes in performance that might have resulted from my mech. changes.