It tracks your mouse movements and graphs it for you.
Here is an image created from me running it for a full day of work:
Click here to see it full size
From what i can tell, a black circle is when your cursor sits idle (the bigger the circle the longer it was idle) and a white circle with a black dot is if it doesn't move for only a short time.
Thought it was kinda cool and wanted to share.
Cheers, The ITG