I have, and my wife tried it as well. It's pretty creative. You just open the app, then put one finger on the digital crown and a countdown timer starts, showing 30 seconds. When you are done, the display on the watch changes and my iPhone dings to say that the results are on the iPhone. What is there is a display of the results for a couple of seconds, plus you can export a PDF for your doctors of the entire 30 seconds. It also assesses the ECG to tell you if it detected afib, or normal sinus rhythm. It also is supposed to alert you if it detects any abnormalities in the rhythm, but I've not had any alerts at all. I don't have heart problems, so I'm happy that it detected normal sinus rhythm. Ditto for my wife. My SIL has afib, I may have him test it next time I see him. Overall, I think it can be useful. I read one review where a woman tested it in her doctor's office while connected to a professional EKG machine and they both detected an abnormality that she did not know she had of an "early" heartbeat. Not dangerous at this time, apparently, but something she didn't know about and that needs watching. Her doctor was impressed.