This is a scientific tool. This app allows for high-precision monitoring and recording of the different sensors embedded on an iPhone.
Supported sensors include:
Gyroscope (rotation rate along 3 axes @50Hz)
Accelerometer (acceleration along 3 axes @50Hz)
Magnetometer (magnetic field along 3 axes @50Hz)
Barometer (air pressure @~1Hz)
This app features "live windows" where you can easily see past motion data.
In addition to a nice visual layout, this app provides a "record" feature, which will record the currently selected motion data and export it as a CSV.
Future updates will include landscape orientation support, and maybe even some "MultiPeer" data aggregation.