I bought this Fitbit Charge as an upgrade from my original Fitbit flex. I wanted something that could monitor my heart rate throughout the day, and this has done a great job. I've worn this running while also wearing my Garmin Forerunner 225 to compare the accuracy. For the most part, this tracks my HR very closely to the Garmin. The only issue I have is that if I run for extended periods of time, the heart rate monitor on the Fitbit stops working. If I remove it for 30 seconds or so, it starts working again. I also like this Fitbit vs the Flex for the display. I can get a real-time view of steps, heart rate, and the time. I also bought one for my mom, and she is becoming addicted to counting her steps!