So I carry my S4 every day and recently activated the fall warning. I work in the radio, running the morning display. It happened to be my birthday that day, and my cohost told me it's a surprise for me to be played on air. Now Cartwall is a block of virtual pads on the airsoft software. You can assign different sounds to each pad and, if necessary, just click it to play. And since I run the desk, I had to click on it. I'm not surprisingly very often, so in the air I was a little anxious. Until my colleague told the listeners and I that this is a surprise. I play the file and it turns out to be a personal birthday greeting from one of the bands. We go off air, bowl and clamps happen, and then I feel. Tap loss, tap loss, on my wrist, with high heart rate warning and question "have you fallen?" I almost pushed the emergency SOS button. 🙂 TLDR: My S4 assumed that my combination of faster pulse and clamps due to surprise at work was enough for slower heartrate warning and fall detection.