AS COMPUTERS continually shrink, the era of wearable devices is nigh. Nike’s FuelBand slips over your wrist to track the amount of exercise you do. Google Glass is a head-mounted display similar to a pair of spectacles that can be sported by the always-online. Apple is thought to be working on a wristwatch-sized sidekick for its smartphones. And from Taiwan comes another example: a tooth that monitors what your mouth is up to.

This might seem an odd thing to want to do, but Chu Hao-hua and his colleagues at National Taiwan University believe there are uses for a device capable of “oral activity recognition”—in other words, monitoring such things as chewing, drinking, speaking and coughing. In particular, it could have medical applications: recording the amount of coughing caused by respiratory problems, for instance, or tracking how much munching someone does when he is supposed to be on a diet.

To test the idea, Dr Chu and his colleagues built a set of tiny accelerometers, which measure movement. Eight volunteers had one of the devices fixed to a tooth with dental cement. They were then asked to do things like coughing continuously or drinking a bottle of water while the team took measurements.

The results, to be presented at the International Symposium on Wearable Computers in Zurich on September 11th, show that people talk and chew in different ways because their mouths and teeth are different. However, if the system is trained, it can recognise what that mouth is doing 94% of the time.

The next step is to make the device easier to wear. One way, at least for those who do not have a full set of natural gnashers, would be to incorporate it into an artificial tooth that might be part of a set of dentures. At the moment, the sensor is attached to the outside world by a thin wire. This carries electricity in and data out, but it is inconvenient to have to walk around all day with a wire sticking out of your mouth. If it were part of a set of dentures, though, the sensor might be fitted with a small battery that could be charged up overnight, when most wearers of false teeth remove them, and thus not need the wire for power. Data might also be extracted from the tooth at this time. Alternatively, information could be relayed directly from the mouth by incorporating a wireless link into the sensor—using Bluetooth, of course.