It's the largest organ we have, and yet our skin's health often goes unchecked. The La Roche-Posay My Skin Track UV Sensor is out to change that. Roughly the size of a Skittle, it clips onto your clothing to measure and track your personal UV exposure. The companion app also provides info on pollution, pollen, and humidity, based on your location, and provides personalized tips to help keep your skin in great shape. Of course, it's not going to do much good if you can't wear it to the places where you get the most sun — like the pool or the beach — so it's also waterproof and thankfully battery-free.