The Mindfulness Bell rings periodically during the day, to give you the opportunity to hold on for a moment and consider what you are currently doing, and in what state of mind you are while you are doing it. According to the Zen Buddhist teacher Thich Nhat Hanh, this is an effective means of developing mindfulness.
If you wonder where the "menu button" is: it is the three little dots in the corner of the screen, next to the "back", "home" and "switch apps" button.
