Fitness wearables are one of the very few categories that have seen the explosive adoption, growing from zero to tens of millions in sales in less than five years.

And it’s the smartphones we have to thank for the rise of this sector – they have fueled the growth by making components cheap, and by enabling apps that created the engagement (e.g., gamification, competition, support, coaching) consumers need to meet their goals.

Fitness wearables have matured from a “fun to have” gadgets to a category impacting the financials of entire industries.Analysis based on Forrester’s Technographics online benchmark survey shows that today in the U.S., 21% of online adults use a wearable device. The high adoption of Fitbit within that group can be attributed to a combination of its hardware and software, with the latter component playing a more pivotal role in Fitbit’s success. It is the mix of technologies that includes machine learning and the added apps layer creates a winning formula.

The result, according to Forrester, is that fitness wearables have matured from a “fun to have” gadgets to a category impacting the financials of entire industries. For example, health payors and providers are starting to imagine the impact of more active members on the bottom line. And in that sense, it is expected that the sales of fitness wearables targeting a broad audience grow for years to come.

Smart watches are not really in the same league as activity trackers. These products have been but have yet to reach the tipping point. Apple is a story for itself as it is able to engage its loyal customer base in a short period of time, the fact that helped it reach the top spot in this product category. Forrester believes the Cupertino-based giant will keep growing in the years to come, with subsequent Apple Watch releases likely having a lower price tag. Meanwhile, other players will also figure out the best use cases for an on-wrist device.