Self-tracking your health data

When you were growing up, the closest you ever got to a personal medical data-collection device was probably a thermometer, or a bathroom scale. But these days, health trackers are a lot more sophisticated – and a lot more wearable.

Smartwatches from companies like Fitbit and Apple are teeming with tiny sensors that display their findings on your smartphone. They can track heart rate, irregular heartbeats, blood oxygen levels, noise notifications, and even hand-washing. And, of course, your pulse rate.

Dr. Sumbul Desai, vice president of health at Apple, demonstrated to correspondent David Pogue how an Apple Watch can warn you about dangerous sound levels, measure your cardio fitness, and even perform an electrocardiogram.