How you'd get the results into a PC tho - dunno!
i do, but its expensive.
you could build your own device using a micro-controller + infra-red, and read the data on a serial port or USB.
the hardware would cost arround $100 (that is due to the micro controller)
the advantage is that it could be re-used anytime to preform other tasks. (like adding function buttons to the bike)
also you can for another $10 add motion detection which outputs Z/X/Y acceleration.
i've studied robotics for a few weeks :-P