Gear up for a giant advance in fitness-tracking devices

San Francisco

SENSORS that track steps, pulse, diet and more marked a wearable computing fashion trend this year as they evolve from measuring what we've done to telling us what to do.

Smart bracelets, watches and pendants increasingly adorned the techno-chic; for some, even their dogs sported medallions tracking whether they nap too much and run too little.

Data gathered …