My mom was excited and confused when she opened her Apple Watch at Christmas a few years ago. “What a nice gift!” A pause. “What am I supposed to do with this?” We told her the truth: A smartwatch can do all kinds of useful things. Fitness tracking became the thing my mom latched onto. She loved counting her steps and seeing how many miles she walked in a day. It motivated her to become more active, too. We didn’t tell her until much later that the Apple Watch’s fall detection feature was the real reason we got her the watch. The feature worked, too. On the coldest day of the year,...