In 2013, Fitbits, Jawbone UPs, and Nike FuelBands accounted for 97 percent of all smartphone-enabled activity trackers sold at brick-and-mortar stores or through big ecommerce sites, according to NPD Group, which tracks the digital fitness device market at the point of sale. For the 52-week period beginning in early January 2013 and ending in early January 2014, Fitbit's devices accounted for 68...
