I met a friend a couple days ago and he was wearing the new fitbit charger 2.
It tracks steps, heart rate (with different degrees of accuracy depending on your type or workout, but it also tracks REM sleep, and how much sleep your getting, as well as other things. Calories, and GPS tracking.
I'm tempted to buy the fitbit charger 2 just to keep track of these things. Not obsessed, but keeping track.
I know that this "bell & whistle" is not needed but it tells you what you're doing and how much. It's interesting.
I've been using "Myfitness pal" to get some kind of gauge of how many calories I'm getting in per day. It's helpful.
If one wants to lose fat or gain muscle, they need to have a gauge of total daily Macro (cals).
Does anybody have a Fitbit?
Here is a good review which shows in detail, all of its features.
Here's an out of the box review.