Org-pomodoro introduces an easy way to clock time in org-mode with the pomodoro technique. You can clock into tasks with starting a pomodoro time automatically. Each finished pomodoro is followed by a break timer. If you completed 4 pomodoros in a row the break is longer that the shorter break between each pomodoro. For a full explanation of the pomodoro technique, have a look at: http://www.pomodorotechnique.com