Minimalism at its best: The Da Vinci Alarm Clock by Marc Owens.

From the website:

The Da Vinci Alarm Clock works on a very basic system. The Dot Matrix display will always show either Sleep or Awake. When the product is first switched on the display will immediately show the word Awake. This will continue to be displayed for 3 hours at 30 minutes. At this point the clock display will change to show the word Sleep and a high-pitched alarm will signal this change in state.
This will continue to sound until the user presses the alarm-reset button.

The word sleep will continue to be shown for the next 30 minutes, at which point the display will revert back to show the word awake, the alarm will also sound at this point to signal that a change in state has occurred.

The 4-hour cycle will repeat itself six times over the course of a 24-hour period and will continue to do so until the clock is switched off. If the user follows the directions given by the clock then they will be able to enjoy the benefits of a 21-hour day, with little of the associated tiredness they would normally experience