New glassware has a sensor that measures the electric capacitance of the vessel and signals when it drops. Since capcitance is a function of the amount of liquid in the glass, this allows the glass to signal when it is empty, which means an end to trying to flag a waitron when you're running low on potables.
Each glass in Mitsubishi's system is tagged electronically by a microchip linked to a thin radio-frequency coil inside its dishwasher-safe base. A coating of a clear, conducting material makes the glass behave like a capacitor – a device that stores electrical charge between two conducting plates separated by an insulator. In this case, the drink is the insulator and the glass's base and sides are the conducting plates.
This is what allows the glass to measure how much you have drunk. When you have had a few sips and the level of the drink starts to fall, there is less of the glass's surface in contact with the insulating liquid. This lowers the capacitance of the glass.
(via Smartmobs)
