Updated 12/13/17: iOS 11.2.1 has just been released, restoring remote access in HomeKit.
iOS 11 is the biggest change to Apple’s mobile operating system in years. It’s so ambitious in scope that some of it’s its most interesting features didn't make it into the initial release. iOS 11.1 mostly fixed bugs and brought us a bunch of new emoji, but iOS 11.2 is more substantial, with the addition of Apple Pay Cash.
After six beta releases, Apple made the unusual move of pushing out iOS 11.2 over the weekend, because it fixes a nasty bug whereby apps that trigger daily notifications could cause your iPhone to crash starting on December 2.