Run the application, turn off the display and leave the phone on his bed during sleep. It will measure all shocks and save them to a file sleep.log on the memory card. The file can be viewed or let him handle in any program (Matlab, Scilab, Gnuplot, ...).

Possible problems:

Do not measure
Apparently, the phone does not have a gyroscope.

Do not measure over off displays
This may happen on certain types of telephones. Tell me the name of your phone.

Where to store the measured data?
In the file "/storage/sdcard0/sleep.log". On the device, it may be, for example. "Internal storage / sleep.log" or "/storage/emulated/0/sleep.log".