An Apple Watch with a cellular connection, paired with Airpods, fulfills some of the role of a small iPhone - you can make calls, listen to music, and even do some light texting if Siri likes your accent.
I love my apple watch but I can safely say i've never done any of the above with it. It's too much of a pain to switch the bluetooth headphones to it and the screen is too small to do much actual computing with it. The fitness aspects are totally worth the money, though.
