Fitbit released its Charge 5 fitness tracker with a brand new design and a color screen in September, but it launched without two key software features: an electrocardiogram (ECG) app and Fitbit’s new Daily Readiness Score, which recommends how hard you should work out. More than a month after the Charge 5’s release, those features are now rolling out.

The ECG app takes a reading of your heart’s rhythm to assess for atrial fibrillation. To take the reading, open the app, put your fingers on the stainless steel panels on each side of the Charge 5, and wait for 30 seconds.

ECG apps are showing up in more wearables, including Fitbit’s own Sense smartwatch and the Apple Watch, but you shouldn’t take readings from the apps as a definitive diagnosis of atrial fibrillation. Research has shown that the Apple Watch can flag multiple types of irregular heartbeats, for example, so if you have any concerns about your heart health, consult a doctor.

The new Daily Readiness Score uses data tracked by your Fitbit to recommend a level of intensity for your workout that day. Your Fitbit device assesses your activity, heart rate variability, and sleep to calculate the score. A higher score means Fitbit thinks you can take on a more intense level of activity, while a lower score means you should prioritize a lower-intensity workout to help with recovery.

The Daily Readiness Score is a Fitbit Premium-exclusive feature, so if you want to use it, you’ll have to be a member of the $9.99-per-month (or $79.99-per-year) subscription service. It’s supported by more Fitbit devices than just the Charge 5, though; it’s also available on the Fitbit Sense, Versa 3, Versa 2, Luxe, or Inspire 2 starting Tuesday.