Staying active is a big part of staying healthy, and that's often the reason given for why you should wear a fitness tracker; they're a constant reminder to get up off the couch. But stress can be just as detrimental to your health as sloth, so Garmin hopes its new vívosmart 3 will finally quantify what you already know: You need a holiday. Besides all the features we've come to expect from a fitness tracker, the vívosmart 3 has a stress tracker built in too.