Fitbit on Monday announced two new fitness trackers with sleeker looks, more durable construction and greater data-gathering capabilities. The Fitbit Charge 2, priced at $149.95, features continuous heart-rate tracking. It uses the data to generate a cardio fitness score and provides guidance for improving it over time. The Charge 2 displays real-time exercise stats, connects to the GPS in a smartphone, and has a set of advanced sensors that make it easier to track activity throughout a day.