A study published in The Lancet has concluded that Fitbit use was associated with significant improvements in a technique used to detect influenza and similar conditions. This is due to the heart rate- and activity-monitoring features in these wearables. Therefore, fitness trackers may play a greater role in public health in the future.
https://www.notebookcheck.net/Fitbit-use-may-be-used-to-help-predict-flu-outbreaks-study-finds.450876.0.html