Tapsy is a watchface for the WIMM One platform, which makes it an Android project.  Tapsy uses the NumberPicker widget from the WimmWidgets project as well.  Tapsy also uses the android support library v4 from Google to use the ViewPager framework.

Tapsy helps you keep track of your blood alcohol concentration while out drinking.  It uses the Widmark formula to estimate your blood alcohol concentration based on your weight, gender, how many drinks you've had, and how long you've been drinking.  It also allows you to set the BAC level to consider "safe" and will show you the estimate time until your BAC falls to that level.  Obviously these calculations are quite rough and are based on a number of assumptions.  You should not rely on Tapsy to tell you if you are safe.  Only you can make that decision.