I didn't think I'd find my Apple watch very useful, but it actually is. In situations where it may be awkward to take out (or even carry) your phone, the watch can act as a mini-phone. Going on runs without a phone is very liberating, while retaining the ability to track your run and stream music to Airpods. It does a decent job of tracking pool swims as well, thanks to being waterproof.

Not life-changing, but adding enough convenience to be worth it.