Thinking of getting a smart watch. What should I expect?

Sorry if this is against the rules, but I'm absolutely clueless in this stuff and would appreciate any guidelines.

The two reasons I'm thinking of a smart watch are: 1)I go to the gym, and I like the idea of listening to music while leaving my phone behind. And -more importantly- 2)I can't bring my phone in to work with me, so that's 8 (or sometimes 12 hours) away from my phone. Having some apps and maybe audio books would be great.

So what sort of functionality can I get if my phone's far away? How's the app capability? I appreciate any guidelines! If it matters, my phone is an honor 8. I've looked at some price ranges and I don't think price is too much of a problem at the moment.