Fitbit Charge 2 And Flex 2 Unleashed: Specs, Pricing And Everything You Need To Know About These Fitness Trackers Fitbit launched two new wearables to replace its most popular trackers, introducing the heart-rate-tracking Charge 2 and the fully waterproof Flex 2. Both gadgets are now available for preorder, so here's what they have to offer. by Alexandra Burlacu