It\u2019s Sunday afternoon at your favorite watering hole, and there are five minutes left in the fourth quarter. Your team\u2019s up by a touchdown\u2014which you missed while waiting in line for the restroom. Now your beer glass is empty, and it looks like it\u2019s going to be a while before the waiter makes it back your way. Do you take your chances at the crowded bar, where you can\u2019t see the screen, or do you watch the final minutes sans libations? If Robert D\u00bfrr has his way, you won\u2019t have to choose: A sensor-equipped coaster will ensure your drink is refilled before you can say, "Super Bowl XL."D\u00bfrr, a computer-science student at Saarland University in Germany, and Matthias Hahnen, a former product design student at Saarbr\u00bfcken School of Arts, have created a coaster-like device that can alert bartenders when their patrons\u2019 glasses need refills. The devices are embedded with sensors, which can record the weight of a glass placed on top of them. Radio transmission units called Smart-Its, created by the Swiss Federal Institute of Technology, read measurements collected by the sensors and send them to a basestation that\u2019s connected to a host computer. \u201cA terminal behind the bar shows where the empty glasses are,\u201d D\u00bfrr says, and alerts the bartender.Other applications for the technology include interactive voting (lift an empty glass from the coaster and return it to vote yes; turn the coaster over to vote no), and teaching beginners the basics of dancing or gymnastics (because the sensors measure gravity as well as weight, the device can be attached to a person\u2019s clothing to record and analyze their movements).D\u00bfrr and Hahnen conceived the smart coaster for a cooperative class offered by their two schools. It is made of plastic foam. Ordinary coasters that provide advertising and absorb moisture can be secured on top of the device.To date, the duo has received a number of inquiries from vendors that want to license and produce the device, but they haven\u2019t accepted any offers.