The following picture is an interesting LED lamp, which is designed by Young Bok Kim. This lantern concept puts a modern twist on the ancient hourglass by draining the light from LEDs instead of sand.

By adjusting the dial in the center, we can control how fast the light "flows" from top to bottom. However, we can't see it as being all that practical because it would be hard to tell precisely how "full" the bottom is getting. Still, it would definitely be cool as a conversation piece.