Fitbit, Nike Fuelband, heart rate monitors, and other gadgets are all great motivational tools. Their value is dependent on individual need, want, or desire. I have used, and use many, but I consider the client’s amenability and the desired goal.
I have also found that certain people get transfixed on bells and whistles to the point of ineffectiveness. As a trainer you want to tap into your intuition in deciding when to hold and when to fold.