https://www.theverge.com/2018/3/13/17113096/fitbit-watch-period-tracking-wearable-fitness

Fitbit’s new smartwatch Versa isn’t being overtly marketed at women. Doing that might alienate its male customers, who currently make up more than half of Fitbit’s user base. But today’s Versa launch coincides with plans for a new app feature that is very clearly aimed at women: period tracking. It’s yet another attempt by Fitbit to draw users into its ecosystem even as the company struggles to maintain its lead in the wearable market.

Here’s how Fitbit’s period-tracking feature is supposed to work when it rolls out in April: it’s free and will work not only on the Versa watch, but on the Fitbit Ionic watch and in the mobile app as well. If you indicate during the Fitbit onboarding process that you’re female, the app will ask if you want to opt in to tracking your menstrual cycle. Once you do that and begin telling the app when your period starts and ends, the app will show your predicted period week as pink, and your predicted fertile window as blue.