Spending on wearable devices in the US nearly doubled in 2015 from 2014, according to the NPD Group, a research firm that tracks sales of consumer products. NPD estimates that 13.4 million connected activity trackers were sold in the US in 2015, up from 7.2 million in 2014, totaling $1.46 billion in sales, up from $692 million the previous year.

These numbers, of course, are still relatively small compared to the number of smartphones in the US, but show that consumers are at least interested in giving wearables a chance, even if studies have shown that some people stop using the devices after a few months. In fact, the NPD data shows the jump in sales despite the fact that the average price of these devices jumped up from $96 to $109, signaling that demand is increasing even as prices go up.

What's more interesting is the new report's findings around market share and category awareness during the year that Apple released its first wearable to the world. Awareness of smartwatches as a category grew, "which bodes well for future growth once newer second-generation smartwatches with cellular connectivity" and more "traditional watches with notification capabilities" are released this year. According to data from another research firm, Apple claims more than 50 percent of the smartwatch market.

But overall, smartwatches still trail lightweight fitness trackers in terms of growth. NPD estimates that nearly 33 million fitness trackers were out there in the wild by the end of the fourth quarter of 2015 (though, not necessarily being worn —see earlier point), compared with 13 million smartwatches. And Fitbit still holds a whopping share of the activity tracking market, accounting for 79 percent of sales.

So, in short, the Apple Watch made more people aware of smartwatches, but didn’t hurt fitness trackers as much as expected. The wearable market is growing, and more people are buying them; they're even willing to spend a little bit more on them. But wearables are still not totally mainstream, and have a long way to go before they achieve must-have status.