A beer mat that knows when a glass is nearly empty and automatically asks for a refill has been created by thirsty researchers in Germany.

Andreas Butz at the University of Munich and Michael Schmitz from Saarland University came up with the idea while out drinking with their students.

The disc-shaped mat can be attached to a normal beer mat so that it still soaks up spilt liquid and displays an advertisement. But it also contains a pressure sensor and radio transmitter to alert bar staff of the need for a refill.