This application is originally created to track our crunches sets in gym, but you can use it generally for track any timed exercise or something that is repeated in same time intervals.
You can set series length (first button), rest count (second button), which is time between series, and series count (third button).
After pressing the start button, scenario is simple. Five seconds to prepare and the first set is started with horn sound. After the horn sound there is specified number of sets and between the each of them, there is rest time. The ending of rest time is signalized same as you hear at start. 4 beeps to prepare and horn sound to start. Every set is finished with triple bell sound.