> Knowing the number of steps you take is also irrelevant unless it's part of some very slow burn exercise regime you're on, in which case you'd presumably count them anyway. If you're doing normal exercise, steps and heart-rate may be of interest, but only during the exercise period.

Fitbit assigns me a goal of 10,000 steps per day. I can view the data and work to reach that goal. By being more active I burn more calories, allowing me to lose weight.

Gamification in service of nudging people towards healthier behaviors has value. It's a means to an end. Sometimes just having a concrete goal with a progress meter is all it takes to get a person to make a small but important change.