Fitbit shipped about 4.4 million wearables in the quarter, a huge increase over the 1.7 million it moved a year ago. But due to the emergence of Apple and Xiaomi (which shipped 3.1 million wearables in Q2), Fitbit's market share slipped from over 30 percent down to 24.3 percent. Overall, Fitbit, Apple and Xiaomi were the top three manufacturers, with Garmin and Samsung rounding out the top five. The emergence of Apple and Xiaomi combined with Fitbit's gains contributed to overall market growth of 232 percent year-over-year. Outside the top five, IDC's "other" manufacturers category grew from 2.6 million to 5.7 million, a clear sign that companies big and small are taking advantage of this new market category.

Apple's position looks even stronger when you look at devices it more directly competes with -- IDC has a "smart wearables" category that tracks devices capable of installing third-party apps. In that segment of the market, the Apple Watch dominates: IDC estimates that two out of three smart wearables shipped in the quarter came from Apple. That's despite the fact that the Watch sits at the high end of the price spectrum. There's likely some post-launch excitement that drove those numbers, so we'll have to wait and see if Watch sales keep growing throughout the year. Cook said on Apple's recent earnings call that sales of the Watch were accelerating post-launch. How long that trend can continue remains to be seen.