Agree with Genghis. Sounds like a great student project.
The key to success may be identifying the right question - an appropriate subject for the iphone.
In the industry we rarely generate 'random' data sets. The recording of vibration parameters is a costly business and is usually instigated as part of a risk-driven exercise to better understand or confirm the understanding the environment of a certain (usually very specific) piece of equipment or location.
I don't subscribe to flyt3ests general post stating that the iphone is inadequate. 10Hz-10kHz is a fairly standard range for aircraft measurements. However, depending on the subject of interest, and the fact that you don't need to sell the results to the FAA or EASA, I am sure you could find a more suitable frequency range. For example, you wouldn't want to use fltt3ests 0-10kHz setup to measure low frequency undercarriage vibration during touch-down as the system sensitivity needed to capture useful data at 10kHz would inevitably result in saturation at lower frequency (higher G) conditions.
Component suppliers will also be uninterested in any frequency above 2-3kHz as the energy involved is so low there is negligable risk to the equipment. Typically, component testing will not go above 3kHz for this reason (as well as test limitation). So even though data may be available to 10kHz, the upper ranges will never get looked at.
The 3 - 10 kHz range is really only of concern to engine mounted equipment and even then generally only concerned with gearbox or fuel system associated equipment that my be affected by gear meshing or pump pressure pulsations. Structural damping sees that these high frequencies don't propogate far through the structure. HP spool fan passing frequencies will also fall into this range but would not propogate any distance through the structure.
It may be 'ride quality' that would be the best application for the iphone. The human body doesn't respond to these high frequences either and robust data is only needed upto a couple of hundred Hz to be useful. If you are looking at the taxi case in particular, then an assessment of the human impact of aircraft vibration may be an acceptable topic.
Good thread! Let us know how things progess.