Google will start rolling out the Fit app’s camera-based heart and respiratory rate trackers on Monday, March 8th. The tech giant first revealed the new features, which rely on the power of a phone’s camera, at a Health event in early February. Both trackers will give you a way to measure your pulse and breath rates even without a wearable sensor, though they’re only making their way to the Fit app for Pixel devices worldwide for now. 

To use the heart rate tracker, you’ll have to hold your finger over the rear camera and apply light pressure — the app will calculate your heart rate by looking at tiny changes in color under your skin. The respiratory rate tracker is a bit more complicated to use, because you’ll have to make sure that the front camera has a good view of your torso for around 30 seconds. You’ll have to prop up the phone on a stable surface, sit and make sure your head and chest are in the frame. The feature then calculates your breaths per minute by measuring the small movements your chest makes.

It remains to be seen how accurate the trackers are: Things like hats, masks and loose clothes could affect the respiratory rate tracker’s results, for instance. If you think they could be useful but don’t have a Pixel device, you’ll just have to wait for the wider rollout. Google promises to expand their availability to more Android devices in the future.