Keep up your activity with the Fitbit Charge 4 Health & Fitness Tracker. Offering a battery life that lasts a full week, this watch ensures you don’t go a day without knowing how far you’ve walked. Additionally, it connects with Spotify so you always have your favorite music close at hand. And that’s not all that comes with this new activity tracker: it even has built-in GPS. That way, however far along you are on your run, you know exactly..