Smart drink coasters are a pervasive computing project form Sentilla. These coasters know when a drink has been placed on top of them, and whether or not that drink is empty. They can even notify the barkeep if you've run out.
Obviously, you wouldn't create smart drink coasters without first creating a coaster software development platform for building coaster applications.
We fired up our Java development environment and started writing a bunch of coaster libraries (ah, we now have a com.sentilla.coaster.* package to import). All in all, our libraries took a few minutes to write and quickly other Java developers in house were modifying, adding, and refining the libraries. One library, our favorite right now, is called CircleCoaster. Very simply, it sets which lights are on, which ones are off, and then the coaster goes to sleep until the next segment of the circle needs to be lit up, thereby making the LEDs light up in a continually moving circle pattern. We didn't stop with CircleCoaster; we wrote libraries to collaborate (in one case, the coasters all display a single pattern on the LEDs when the majority of coasters have drinks placed on them and a different pattern when they don't) and play games.
Although I can't name any smart drink coasters in science fiction (can you?), this application does make me think of the monoblock dating system, which is another network application running in pubs, from Larry Niven's The Best of All Possible Wars story collection.
Nobody hurries in the Monobloc. If you see someone you like -" My fingers danced over the lighted symbols on the edge of the table. "This gets you a map. Locate where she's sitting, put the cursor on it. That gets you a display...hmm."
(Read more about Niven's monoblock dating system)