this is very neat, and analysis using Wolfram can make it scientific (although the iPhone is not a scientific instrument)

however: as far as interpreting gestures: the iphone has that built-in, the methods are patented, and Apple allows using the libraries for detecting gestures free by the public (likewise, android i think released free code for their lib)

if your goal was iphone gesture, i believe it's already done and patented but available to use - realtime recognition

but downloading raw data and re-recognizing it, nothing wrong with that

HOWEVER: as far as mathematica learning being slow and inaccurate. sound recognition is a MAJOR job: mathematica has a large section for Sound that's good (your gps signal it still applies though your wave form is not in that form). Sound cards have special recognition components that do things CPU cannot keep up with. the best waveform analyzers cost tens of thousands.

i'm unsure if you want quick waveform detection if you should be using the "computer learning" feature. perhaps you should convert it to soundwave form and check your options that way