SeisMac for Mac

From Suitable Systems:

SeisMac turns your Sudden Motion Sensor-equipped laptop into a three-axis seismograph. It shows a scrolling chart of the three axes of acceleration, reading two hundred samples per second.

The resizable, real-time scrolling display shows an enormous amount of acceleration information. Place your laptop on a table, and see the seismic waves from tapping your toe on the floor. Lay your laptop on your chest and see your heartbeat. And, of course, if there is a real earthquake, SeisMac will be displaying full seismic information while you drop, cover and hold-on.

When running on the MacBook or MacBook Pro, SeisMac has a range of plus or minus two gravities of acceleration, displaying 256 values per gravity, sampled two hundred times per second. SeisMac is also compatible with older Sudden Motion Sensor-equipped iBooks and PowerBooks.

SeisMac is free for Mac OS X 10.4 or later. It is compatible with MacBooks and MacBook Pros, as well as Sudden Motion Sensor-equipped PowerBooks and iBooks.