Perhaps as a counter point to yesterday's critique of Apple's HomePod development - if Apple's engineers are too busy coming up with ways to save people's lives with the Apple Watch and have to sacrifice dev time on a talking speaker, I'm generally ok with that:
To calculate heart rate and rhythm, Apple Watch’s sensor uses green LED lights flashing hundreds of times per second and light-sensitive photodiodes to detect the amount of blood flowing through the wrist. The sensor’s unique optical design gathers signals from four distinct points on the wrist, and when combined with powerful software algorithms, Apple Watch isolates heart rhythms from other noise. The Apple Heart Study app uses this technology to identify an irregular heart rhythm.
This kind of stuff, more than checking my calendar or Twitter, is what will convince me to buy and start wearing a watch.