WorkBreak

The purpose of this app is to make you aware of the time you've spent working and the fact that we all can use a break now and then.

You can set up two different durations; one for your work session and the other one for your break.
When the work duration reaches zero, an alarm (the device's default alarm) will fire, notifying you that it's time to take a break.
When the break duration reaches zero, another alarm (same sound, though) will fire, notifying you that it's time to get back to work.
After this the cycle repeats itself until you press the Stop-button.

You can add a variable amount of time to the current running timer when you feel the need for it.