Julie Clothier at CNN:
The “smart” beer mat, created by Matthias Hahnen and Robert Doerr from Saarland University in Saarbruecken, southwest Germany, can sense when a glass is nearly empty, sending an alert to a central computer behind the bar so waiters know there are thirsty customers.
The students’ supervising professor, Andreas Butz, told CNN the plastic beer mat had sensor chips, which measured the weight of the glass, embedded inside.
When the weight of the glass drops to a certain level, the sensor chips detect that it is close to empty and alerts the bartender via a radio signal.
More here.