“Beginning September 23, users will have access to yet another next-generation feature, as on-demand electrocardiogram (ECG) readings come to Galaxy Watch 3 and Galaxy Watch Active2,” Samsung said in a press statement. “This tool recently received clearance from the U.S. Food and Drug Administration (FDA) and will soon be available through the Samsung Health Monitor app when connected to a compatible Galaxy smartphone.”

This tool recently received clearance from the U.S. Food and Drug Administration (FDA), and will soon be available through the Samsung Health Monitor app when connected to a compatible Galaxy smartphone. The new ECG Monitor app allows users to monitor their heart rhythm for irregularities, scanning for signs of atrial fibrillation (AFib).

To use the ECG Monitor app, simply take a seat, open up the new Samsung Health Monitor app, and ensure your watch is snug around your wrist. Rest your arm on a flat surface, place your fingertip on the top button, and your watch will record an ECG and classify it as either Sinus Rhythm or AFib.

Once the reading is complete, users can record relevant symptoms like fatigue or dizziness and send a PDF report of their ECG recording to their healthcare provider using the Samsung Health Monitor app on a compatible Galaxy smartphone.

In addition to ECG monitoring, you can also conveniently track oxygen saturation on Galaxy Watch 3. This feature can help users get a sense of how well their respiratory system is transferring oxygen into the bloodstream for fitness or other general wellness purposes.

It appears that Samsung’s ECG app will operate similarly to Apple’s. After opening the Samsung Health Monitor app, you’ll be advised to put your arm on a flat surface and place your finger on the top button. The watch will identify you as having either a normal Sinus Rhythm or atrial fibrillation. Once the reading is done, you can log symptoms like dizziness or fatigue. (Atrial fibrillation is often unaccompanied by symptoms.) You’ll also be able to send a PDF report to your healthcare provider.

The catch here is that, at least for now, the ECG app will only be available on Samsung Galaxy phones with Android Nougat or higher—meaning, if you have one of these watches paired to a non-Samsung Android phone or an iPhone, you’re out of luck. That’s only sort of surprising. While Samsung’s smartwatches are among the best currently available for Android users, Samsung is like Apple in that it likes to push its own ecosystem. As a result, some features are only available to Samsung phone owners. It looks like, for the time being, ECG is one of them.