All smart watches and sports bands equipped with GPS receivers such as Fitbit Flex 2 can be used as a GPS tracker. It doesn't matter how you connect to the internet - direct (eSIM) or indirect via a smartphone. In both cases, you can track your wearable device online in real time. More information is available on this GPS tracking platform for smartwatches.
This device has pedometer, sleep tracking. You might be interested in some other devices with sleep tracking. If that so, you can find it here.
If you want to track your activity during training, you need a device that can communicate. Fitbit Flex 2 have several types of comunication. For example Bluetooth. The best activity truckers have Bluetooth and you can find them here. More information about wireless communication in activity trackers can be found in our article.