The Apple Watch is the world’s most popular line of smartwatches right now, holding about 50% of the global market. When Apple announced the Apple Watch Series 4 last year, there was one feature that stood above all. It wasn’t the larger display or the Digital Crown with tactile feedback.

Instead, it was the addition of ECG (electrocardiogram) capabilities without any additional hardware needed (besides the Apple Watch itself, of course). The feature allows the user to quickly and easily take an ECG and then, if need be, send the results to their doctor. Even without having the results ...