Fitbit announced its first smartwatch, Fitbit Ionic, which features a new relative SpO2 sensor. The introduction of a relative SpO2 sensor for estimating blood oxygen levels opens the potential for tracking important new indicators about wearer’s health, such as sleep apnea, according to a Fitbit press release.

“Ten years ago, Fitbit pioneered the wearables category with the introduction of its first health and fitness tracker. Since then, we have become the leading global wearables brand, setting the pace of innovation in the category and establishing the largest social fitness network that helps millions of people around the world be healthier,” says James Park, co-founder and CEO of Fitbit, in a release. “With Ionic, we will deliver what consumers have not yet seen in a smartwatch—a health and fitness first platform that combines the power of personalization and deeper insights with our most advanced technology to date, unlocking opportunities for unprecedented health tracking capabilities in the future.”

In addition to new features, Ionic has traditional Fitbit features including: automatically tracking steps, calories, floors climbed, and sleep stages, cardio fitness level (estimated VO2 Max), maintain moments of calm and more.

Ionic is available for pre-sale today online and in retailers globally starting October 2017. The Fitbit app software development kit will be open to developers in September 2017.