It may not be immediately apparent, but the picture you are seeing is that of a clock. The red ball in the cup is the hour hand, while the white one shows minutes. This works because the ceramic base contains two rotating magnets that control the motion of the two floating dots. The cup and plate aren't included in the kit, but that adds to the appeal of this gadget--how the "clock face" looks is entirely dependent on the receptacles you choose to use.
This Water Clock by designer Kouichi Okamoto doesn't come cheap at $299, and unless your home has crazy laws of gravity, you can't hang it on a wall. It's still one of the coolest clocks we've come across and is available from online store Generate Design.