We all know the natural physical signs of dehydration: a headache, a dry mouth, drowziness, and keeping track of hydration can be especially important during the summer months. That’s why Sandia National Labortories has invented a wrist band watch with a sensor that let’s you know when you might need to refill the water bottle. With varying micro-needles that rest on the interior of the band, the needles attach to the skin and measure the interstiltial fluid levels- the water that sits between your cells. When the measurements reach a level below what is considered safe, the watch will notify you to hydrate yourself. If we see an expansion of this device, perhaps incorporated in our everyday smart watches, we may see a revolution in fitness and sports performance all around.