SensorLogger records your iPhone sensors in realtime, including accelerometers, GPS, compass and gyroscopes. Sensor logs may then be exported in an easy to read CSV format, or reviewed on the phone.
SensorLogger can also stream sensor data to a wireless network, as it is recorded. This could be used to control another device on the network in a fashion similar to modern consoles (for instance, by using the high-frequency acceleration data), or to provide the required inputs for a mechatronic project (such as a UAV).
Please note - the compass is only available on iPhone3GS and iPhone4, and gyroscopes