While being able to use your smartwatch as a walkie-talkie isn’t a new concept—the Apple Watch already does this—it’s something new to the Galaxy Watch 4. Specifically, the Galaxy Watch 4 and 4 Classic, with no other models listed at the moment. The new app will let you communicate with other Galaxy Watch users (who also are using the app) directly by holding the microphone button.
According to XDA Developers, while Samsung recommends running the WalkieTalkie app while your watch is connected to your phone, it’s not necessary. If you have the WalkieTalkie app installed, you can just pair your watch with a friend’s (so long as they’re physically close by) using a PIN code. Though if your watch is connected to your phone, you can create a walkie-talkie channel using your Contacts.