Just don't ask them about sharing their health data with scientists. Pew warned that there was "no clear consensus" about the acceptability of sharing info in the name of heart disease research. About 41 percent of respondents considered it acceptable, but 35 percent didn't -- and 22 percent were unsure. Approval shot up to 53 percent among people who did use wearables, but that still left many people wary of contributing to medical science.

The study should be fairly representative with 4,272 participants. It doesn't address why people adopt or shy away from wearable tech, though. Fitness clearly plays a role for many buyers, but it's not certain what holds others back. It may take some time before researchers can say if wrist-worn devices have more room to grow.