I am a member of a soccer club. We have no real goalies there so the field players have to take turns in the goal. I always have the feeling that some people spend more time in the goal then others but I have no real proof. I suggest creating a device similar to a chess clock but with five and more buttons. If you're in the goal, you press your button so as it is easy to track your time there. I am sure that this device would have many other applications!