just looked, my box has a line input so I could feed it audio from my tape deck (in stereo) also has at least two mic inputs(mono). of course it occurs to me that one could, with a little work, use a 'Mr. Microphone' and get the same results as the rocketronics unit . as I recall the guy used a 'button' piezo mic as a pressure sensor, since it wasn't calibrated we didn't know what pressures were reached in the combustion chamber...but he was able to analyze the data down to the millisecond (whole event took 45 ms from ignition to spud leaving the barrel). one could do much the same to get an accelerometer.
looks like one could use 'win voice recorder' to input an analog audio signal. I am reasonably sure that there are other free 'apps' that one could use.
Rex