This teeny, wearable blood flow sensor claims to be able to measure circulation even while you're moving. Most sensors require you to sit still, but with this, doctors can keep track of your condition while you run. Or have a beer.
The sensor was developed by a research group at Kyushu and Tokyo Universities. According to DigInfo, it can detect dehydration in real time, as well as measure blood pressure and detect alcohol consumption. A physician could use it to monitor an athlete's health during activity, or potentially detect diseases. [DigInfo]