Well, what you can do is slap 95% proportion confidence intervals (CI) on your estimate. Next, you can use the CI values to make a statement such as, we are 95% confident the true proportion of persons with a smartwatch is between lower interval value and upper interval value.

This calculation takes into account your sample size. Also, you do not have to use 95% CI, you could use 99% CI, though per logic and the formula, to be more confident you want to be the wider the interval will likely become.