Reliable
Since I do not feel anything when I go into AFib, I have found Photo AFib to be a reliable detector in my two and half years of using the app. Update May 2019: After a year and half of being in sinus rhythm, the app immediately detected that I had gone into AFib. That allowed me to be treated by cardioversion the next day. The app worked accurately before, during and after the AFib episode. Update April 2021: Does not work on my new iPhone SE2. Keeping my old SE just to run Photo AFib Detector.