Tabata Timer is an app for interval training.  It allows you to set intervals, rest periods, and rounds.

This timer is based on the Tabata protocol that was first mentioned in a study published in 1996 by Dr. Izumi Tabata. With the intense interval workout you get maximum workout results in terms of aerobic and non-aerobic capacity as well as fat burning with four minutes of daily exercise only. A result you won’t reach in the same time with any other conventional workout. Each workout session runs over 8 sequences, each of which means 20 seconds workout and 10 seconds break.

Tabata Timer - TabTimer