https://www.cnet.com/news/watchos-5-adds-walkie-talkie-kills-need-for-siri/

Going into Apple's WWDC 2018 keynote, rumor had it that with the arrival of WatchOS 5 Apple would finally allow third-party developers to create and sell watch faces for the Apple Watch. That didn't happen, but Apple did announce enhancements to the Activity app, Siri watch faces, Notifications and a new Walkie-Talkie feature that allows you to communicate directly with other Watch users over Wi-Fi or cellular data. 

Aside from the Walkie-Talkie feature, the biggest update will be the ability to raise and turn your wrist to issue voice commands without saying, "Hey, Siri" first. Raising your wrist automatically activates Siri.