After two years Fitbit has upgraded its popular Charge fitness tracker with the new and improved Charge 2. Its biggest improvement is the new Cardio Fitness Level graph, which monitors how much oxygen your body takes in and uses in one minute. It’s a metric often used as an indicator of an athlete’s overall fitness. But, for the average Joe, it’s a statistic that can be improved upon over time. This Bluetooth-enabled wristband now also has a range of notifications including calendar alerts and messages, in addition to the previous buzzing notification to alert you to calls. The Charge 2 effectively monitors every part of your day, from sleep monitoring with silent alarms to wake you in the morning to regular five-second heart rate tracking with the integrated HR monitor. Also, connected GPS mode allows you to track outdoor exercise, as long as you keep your phone with you, measuring distance covered, whether it's jogging, running or cycling.