"Those of us trying to lose some pounds after overindulging this holiday season can get help from a slew of smartphone apps that count steps climbed and calories burned.
Self-tracking has also become a way for companies to make money using your fitness data.
And some experts worry that the data collected could be used against users in the long run.
At a recent Quantified Self Meetup in downtown San Francisco, technology lovers are testing homemade do-it-yourself devices on people eager to measure their mind and body."*
