On the Medallia blog, Erling Ellingsen has been monkeying around with the accelerometer on the iPhone, some applications of which he demos in the above video. He writes:

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. After a rather lengthy bout of reverse-engineering (I had barely touched ARM assembly before this), I finally figured out how to access the raw data from the accelerometer itself, as can be seen in the video above. Source code is posted here. (update: yes, it is possible to access the accelerometer directly through UIKit without this hack — however, you’ll be locked to the default sample rate, which is too slow for some of the fun stuff)

Fun with the iPhone accelerometer – [via] Link