Canalys' researchers attribute the shifting ranks to the Apple Watch Series 3 launch. Demand was strong enough that there were shortages in "major" markets, including China. And apparently, Series 3's cellular data support is a big draw -- analysts reckon that Apple shipped about 800,000 LTE-capable watches in the quarter. For comparison, Samsung is believed to have sold roughly 500,000 Gear S3 watches (LTE or otherwise) in the same period.

This doesn't mean the wearable space is suddenly red hot. While Apple, Xiaomi and Fitbit did well, Canalys believes the overall market shrank 2 percent to 17.3 million units. As it explains, demand for "basic bands" (that is, entry-level activity trackers) was on the decline. That's likely to be even more true now that Apple is more likely to keep up with Series 3 demand, and Fitbit is getting into full-fledged smartwatches with the Ionic. It's no longer enough in many cases to give people their step count and heart rate. They increasingly expect a full-fledged smartphone companion, and the market is changing accordingly.