"A new sensor, designed to be one day embedded in tooth cavities, crowns, dentures and braces, is slated for an unveiling in September at the International Symposium on Wearable Computers. But you can find a good report on it already in an article in New Scientist.
In a nutshell, the inventors see this tiny mouth sensor as an ideal mode of tracking health intelligence. The sensor is designed to gather data on jaw motion, which the inventors say will monitor the patient for teeth grinding and other dental problems, as well as monitor the impact of dental interventions.
But that same sensor can also detect whether you have been eating too much or too little, or smoking against medical advice. Eventually, it may even be able to pinpoint precisely what you have been eating, drinking or smoking (even, if not especially, non-tobacco products)."
"..But what worries me most is the very real possibility that such devices could be implanted without the patient's full understanding of how the device can be used."