For scientific reasons Robota Softwarehouse made an application on the iPhone that log’s the accelerometer data. Just start the application and turn your phone, even shake it.

You can use this application for your own research, for example to figure out a movement when programming a game. Log how smooth your car drives, etc, etc.

The functionality of the free version is limited to viewing the graphs and changing the sample speed. The full version can be ordered for 199 euro.