Keeping beer mugs filled in restaurants and bars can be a very difficult job. However, the problem may just have been solved by two German students who invented a new "smart beer mat" coaster that keeps track of how full your mug is. According to this report on CNN.com:
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.
This invention definitely doesn't solve world hunger but it does serve its purpose and that deserves some merit. I wonder if this beer mat could send its signals wirelessly? Or better yet the functionality could be built into a beer mug to monitor other characteristics other then just mug fullness. For example, it might be useful to let servers know the temperature of your beer because a warm beer can sometimes be as big of a problem as an empty one. It's be nice for servers to come by with a fresh pint when you are milking a warm one.