Last week I had downloaded this heart monitor app, intrigued at how it used a finger placed over a phone's camera to work out your pulse.
My father was visiting so I showed him the app for fun. He's 86 and has had a few issues with walking etc. but that wasn't on my mind. The app read 36bpm--way low (as Wolfram|Alpha confirms). My wife, ophthalmologist Stella Hornby, checked. It really was 36bpm; she was sure he had a heart block. After some effort we pursuaded him to hospital. They confirmed the diagnosis where this morning he had a pacemaker fitted (rather a quick turnaround by the UK NHS, I thought).
This result is all the more amazing as 3 years ago my wife thought my father might have carotid sinus syndrome, and that a pacemaker would be the likely treatment. But on visiting the cardiologist, he couldn't find anything (heart rate was fine while they were measuring it) and so nothing was conclusively diagnosed, and no treatment given.
What an example of the power of interactive apps and the future of self-monitoring!