Best Overall: TomTom Runner Cardio (Full Review): 16 out of 20 stars

The TomTom Runner Cardio is designed for runners — it has both a heart rate monitor and GPS capabilities that let it track data such as your distance, time, pace and speed. The Live Science testing team determined that this device is also the best overall tracker because it not only has the advanced features of a heart rate monitor and GPS, but it is also supremely easy to use. It has a single, large button that makes it easy to scroll through your data, even on the fly. You can also wear it while swimming. The accompanying MySports app will create charts of your data over time, and also lets you set your own goals for distance, time or calories burned, sending you text alerts to help you work toward them. However, at about $270, the Runner Cardio is pricier than other fitness trackers, and it doesn't track your sleep.