I have a fitbit blaze to monitor my sleep and heartbeat vagueries.
As with the Charge, it has the steps, HRM, distance travelled etc, pretty accurately. I scratch the surface of the fitness side but can see the benefits as a fitness tracker all round health helper, particularly used in conjunction with the smartphone side: analytics, GPS etc.
You can select activities you do, pick up routines and workouts on it. Analyse everything on computer and smartphone via the app and their regular email reports.
Comfy, decent size on a smallish wrist, looks blocky but not garish as a watch and has some smartwatch gizmos, vibration alarm, music controller, picks up messages and calendar alerts, lets you know your phone is ringing - but you can't make/take calls on the wrist.
I like it and could use it far more if I was working out or training.