This is a PC (Windows)-based tool for mob programming.
The way it works is that when the mob is ready to start, each mob (team) member is added (by name) to the mob list using the GUI interface. Next the team decides on what time interval they will rotate and sets the slider to 'rotation time' for this session.
Common rotation intervals are 5 min, 10 min or 15 min.
At the end of the interval, the timer application jumps to 'foreground' process and 'blanks out' the screen. This encourages switching to the next driver mob team member (will be on the keyboard) on the list.
There are also buttons to 'start turn', and others, such as 'skip'. The latter allows the team to skip over drivers as need be.
For more about mob programming, see http://www.mobprogramming.org