Various personalised stats show. Each dot around the circle is a day of the month with the current day highlighted. In the centre it will show things like number of minutes, sms sent/received, photos taken, tracks played, miles walked etc. The balloons around the edge are larger on days when you do more. So you get a personal visual representation of how you use your phone.

Disclaimer (because it seems to upset people here), I work for Canonical ;)