A beer mat that calls for a refill when the pint is almost empty has been invented by scientists in Germany.
The electronic beer mat was created by computer scientists Andreas Butz of the University of Munich and Michael Schmitz of Saarland University.
Beneath the cardboard surface is a small, flat baseplate which conceals pressure and acceleration sensors that react to the weight of the glass and the position and movement of the coasters.
The microsensors then pass on this information via radio link to the bar, where the signal is picked up and decoded by a waiting computer.
The customer can speed the order up by "flapping" the beer mat, and can order more beers by using a stack of mats to express the number of drinks ordered.
The inventors say the thinking beer mat is also capable of more than just ordering a refill.
It could also for example be used to judge the performance of a karaoke singer or to give an opinion on referee decisions on big-screen matches in sports bars.
A "Yes" vote, for instance, could be registered by raising the glass, causing the sensors to move.
A "No" would be registered by raising the glass and then turning the cardboard mat over and replacing it on the baseplate, thus causing a telltale double movement of the sensors.