I have an iPhone 6, got it back when it was released (2014? I think so but I've lost track) because Verizon had a promo at the time where you could trade in an iPhone 4 (which I had then) and get $200 for it via a Verizon Wireless gift card. Since all the other outlets were offering $35 for that phone at the time, I figured it made sense to get the $200. I used it to pay the phone bill for the next few months.
Ms1995hoo gave me the Apple Watch last Christmas. It's very nice at the office for discreetly reading personal e-mail since using your phone at your desk for anything other than listening to music or podcasts is very much frowned upon at my office (we all do it, but doing it more than every once in a while is a good way to land in hot water). I use it frequently for that purpose, although I do not usually respond using the watch because I'm not going to sit there dictating an e-mail. I also do not have all my e-mail set to show up on the watch because that would get distracting—I set it so only the "VIP" accounts (family and our Caps ticket-share group) ding the watch.
The exercise tracker has actually proven pretty beneficial to me—I've lost seven pounds this year. I had lost more but I've gained some of it back in July and August due to the combination of driving to work and parking closer than I used to park due to the hot weather and my wife's office relocating closer to mine. The thing about the movement tracker is that I find I'm better about getting out and getting some exercise, even just going for a good walk, if I have something giving me a concrete goal and tracking what I do. It's easy to say "I need to get more exercise." Having the thing tracking it for me helps. In terms of the text-messaging, the person I send text messages to most often is Ms1995hoo and the message is usually simply to tell her when I'm leaving work so she knows when to meet me at the Metro stop. For that purpose, the pre-programmed "On my way" message is ideal—very easy to use the watch just to send that as I walk to the elevator. I use the timers and the alarm features pretty regularly as well.
Sure, there are other devices that do the same things, but my wife gave me this one for Christmas. It's not essential by any means, but it is a nice little device. It's always fun at the grocery store to use it to pay if there's an old lady waiting on line behind me. Invariably she's baffled when I just hold my wrist next to the credit-card reader for a second or two. (Interestingly, the Coke machine at the office accepts Apple Pay, so I use it there because it tends to eat dollar bills and not give you your soda, whereas if you pay with credit it's more reliable. But our office is moving next week, so that may soon become irrelevant.)