Walkie-Talkie on the Apple Watch is a clever riff on FaceTime Audio
https://www.theverge.com/2018/6/4/17428180/walkie-talkie-apple-watch-facetime-audio-wwdc-2028
After the health app improvements, the headline feature for watchOS 5 at WWDC was Walkie-Talkie, a new app that lets you send and receive quick voice messages with friends and family. Earlier today I got a brief demo of the feature and was surprised to discover that it works a little differently than I expected.
What I expected was a sort of voice message feature, where you record a quick message, send it, and your contact does the same and sends one back. But that’s not how Walkie-Talkie on the Apple Watch works at all. Instead, when you initiate a Walkie-Talkie chat, what you actually get is a real-time FaceTime Audio call that just happens to include push-to-talk (PTT) instead of a full-duplex audio call.