Simple Friction Experiment

Simple Friction Experiment is an app intended for students and Physics' enthusiasts. With this app, it is possible to determine the static friction coefficient with the only aid of a smartphone and a worksheet-based program like Microsoft Excel, LibreOffice Calc or any other capable of importing text files.
Instructions:
Put the smartphone on a flat horizontal surface that could be tilted (like for instance, a hard-cover book). Click on the START button and start slowly tilting the surface (rate of data collection is 2 points per sec) up until the smartphone starts to slip down. At that moment by clicking on the STOP button the user can finish the experiment. If it does not happen in 25 seconds, the app will stop recording data automatically and let the user know by making a beep.
The values of the acceleration in 3 axes (x, y and z) will be shown on the display. If the data plotted is worth to be saved, that can be accomplished by hitting the button SHARE. That will open up a menu with several options available.
The format of the data collected is csv even though the extension of the file generated is .txt.
Further processing of the data is necessary, it requires certain minimum knowledge of Physics.