This is the free version of the app which was developed for researchers so that they may capture accelerometer, gyroscope, and magnetometer data directly from their iOS device to use for research or play around with. The data is time stamped and the data from Apples enhanced device motion is included for reference.
You can only collect data for 10 seconds and the sampling rate is set at 10 Hz. Please buy the non-trial version Data Collection app if you would like to configure your own sampling rate and collect data for indefinite amounts of time!