Doing The Two-Wrist Tango
The idea of having something on your wrist for two way communications seemed pretty cool in the 1960s and the cool factor, for me anyway, is considerably dialed up, as it were, with the Apple Watch. As of the Series 4, it functions as a standalone communications device; you can use it to send and receive text messages, check the weather, and perhaps most usefully, you can get health and fitness information from it in ways you cannot with a smartphone, no matter how smart. Heart rate as well as heart rhythm data can be obtained and even shared with your physician, and you can keep track of everything from how many steps you've taken, to how many calories you've burned over a range of different exercises... More here.
I went the other way. My Fitbit now sits on my belt because I didn't want to do any two wrist thing...