Yes, we'll admit, that it sounds pretty gross and potentially a little too personal. But it is interesting technology. As the video demonstrates with the prototype Nissan Juke, the steering wheel and seats are outfitted with a special cloth coated in a material called SOAK. It looks normal at first, but when you've been sweating a lot, the cloth changes colors depending on your hydration. If you're dehydrated, the cloth turns yellow, and after rehydrating, the cloth turns blue.
Now you may be asking, why is this so important besides general health? Well, Nissan cites a study by the European Hydration Institute and Loughborough University in the U.K. that found dehydrated drivers are as dangerous as drivers with a blood-alcohol content of 0.08, the legal limit both in the U.K. and throughout the U.S. With that in mind, a car company would have some interest in keeping people from driving impaired.
Somehow, we don't see these hydration materials becoming common in cars anytime soon, though. For one, we're not so sure people want their sweat so clearly visualized in their cars, nor do we think many people want to see their upholstery become discolored for any reason. There's also the issue that you can become dehydrated even without sweating significantly, and it seems that this upholstery is very dependent on sweat to work. So if you just haven't been drinking, even without exercising, it's possible you could be dehydrated, even without really obvious signs. But it is an interesting project, and we can imagine the fabric could find a home in athletic wear.