Fitbit has had device-free tracking for 9 months and more of your friends are probably already using it. http://blog.fitbit.com/introduci...

"UP® is a revolutionary system that guides you every step of the way to a better, healthier you. First, UP gets to know you—tracking your activity, diet and sleep. Next, it shows you how to make simple adjustments that, over time, add up to a whole new you. No UP or UP24 wristband required."

I have a band, and use the software. Using without the band should be nice. App UX is great except for the little 'factoids' they give you. The software doesn't let you dismiss them or close them, only report (which seems excessive). Additionally, the sleeping functionality is apparently faulty, and they don't really tell you the difference between 'deep' and 'light' sleep. Overall not bad if this thing is your cup of tea.