Tabata Timer is an app for interval training. It allows you to set intervals, rest periods, and rounds.
Version 1.2 adds a wakelock to prevent the app from sleeping, changes the whistle to a loud bell/buzzer, and adds a countdown timer.
Version 1.3 fixes the force close issue many people running Android 2.2 or above have been getting.
This will be the final free version, next one will have more features and be paid.