According to a recent report from the NPD Group, San Francisco-based Fitbit shipped 67 percent of all activity tracking devices in 2013. The company's devices also accounted for 77 percent of the "full body activity trackers" shipped during the five weeks leading up to Christmas. That's up from about 60 percent for 2012's holiday season, according to Fitbit. NPD also estimated that the digital fitness category is now a $330 million market.

It's not entirely clear what NPD considers a "full body" activity tracker is and which devices may be excluded from the definition. However, considering Fitbit devices are stocked in more than 20,000 North American retail stores and a total of 30,000 stores around the world, it's no surprise their numbers for shipped devices are so high.

Overall, NPD found that fitness trackers as a category were more than three times as popular this past holiday season than they were in 2012. This past holiday season saw 3.1 times as many devices shipped year-over-year, according to Fitbit and NPD.

The company announced the data from NPD's report just as the big CES event in Las Vegas was getting underway. Many new and updated activity trackers are set to launch at the event. Fitbit, however, has not announced a new device at CES, likely because it just announced its latest wristworn tracker, Fitbit Force, in early October. The company has a range of fitness trackers starting with the relatively inexpensive clip-on device, Fitbit Zip, which costs about $55.

Fitbit did announce a partnership with designer Tory Burch to create new accessories and also announced that its devices would connect to a dozen additional Android smartphones, including Droid Mini, Droid Ultra, Droid Maxx, Droid Razr M, Droid Razr HD, Droid Razr Maxx HD, HTC One, LG G2, Moto X, Nexus 4, Nexus 5, and Nexus 7. Fitbit first began wirelessly synching to Android devices last February.

NPD Group also released results from surveys it conducted for the study, which found that one in three consumers say they have heard of wearable fitness trackers. Of that group, about 28 percent said they were likely to buy a device. Half of them said counting calories is the most sought after feature and 32 percent said tracking steps was the most desirable feature. Only 6 percent had an interest in sharing their fitness data via social media. Slightly more (58 percent) women were interested in buying the trackers than men.

“According to The NPD Group’s Retail Tracking Service, the digital fitness category has grown to over $330 million,” Ben Arnold, executive director, industry analyst The NPD Group stated in a release. “The market is now large enough to accommodate a variety of products aimed at all levels of athlete -- from serious performance-minded consumers to hobbyists --a sure sign of maturity.”