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.

“You could have hundreds of beer glasses in the bar and the beer mat would, for example, tell the bartender, ‘table 14 needs a refill,’ ” Butz told CNN.

Unlike the usual cardboard beer mats, the invention is made out of plastic, which means it does not absorb water.

Butz said that to get around the problem, ordinary cardboard mats could be placed on top of the plastic version to absorb liquid and display advertising.

“Cardboard beer mats could still sit on top of the plastic mat and there could still be advertising, and you would just exchange the cardboard mat when you wanted to change the advertising.”

The chips inside the mat also measure gravity, and know when the glass has been turned upside down, Butz said.

This could be used as a “voting system” during karaoke competitions: patrons could raise their glass if they liked a singer, or flip it over if they did not, Butz said.

“You could argue that the voting system is more likely to be positive because people would be sipping their glasses during the course of the song but this would just add to a more positive atmosphere in the pub,” he said.

Butz, who now works as professor of computer science at the University of Munich, specializes in human computer interaction. He and Michael Schmitz, of Saarland University, presented the idea at the International Conference on Ubiquitous Computing in Tokyo earlier this month.

Butz believed it had potential to become a commercial reality.

“It’s a funny idea but the nice thing about it is these students have followed it through right to the end. They’ve come up with the idea but they have made it practical — it is even dishwasher-proof,” he said.

More here.