Erling Ellingsen figured out how to retrieve high sample rate measurements from the iPhone’s built-in accelerometer:
As it turns out, the iPhone has a built-in LIS302DL, a tiny 3-axis accelerometer. While some have attempted to use it from within the Safari browser (the Tilt game detects changes to the width of the browser page; it is basically used as a 1-bit input device), its potential is still somewhat untapped.
He’s posted the necessary source, so now you can get to work on your own motion-input applications.
iPhone accelerometer source code – Link