The just-released watchOS 5 has a new feature called Walkie Talkie, which lets you have a one-on-one conversation with anyone who has a compatible Apple Watch.
The Walkie Talkie app is located on the watch’s home screen. It’s indicated by a yellow icon that looks akin to, well, a walkie- talkie.
Open the app and a list of contacts that have an Apple Watch who you frequently FaceTime or iMessage pops up. You can add another contact card by scrolling to the bottom of the list and selecting the "+" symbol. An invite will be sent to the contact who can accept (or note) your Walkie-Talkie friend request.
You can delete a contact from the app with a swipe to the left on the contact card, then tap on the red "X."
To start a Walkie-Talkie conversation is simple, choose a contact in the app, press and hold the Talk button, speak your message, then let go. The person on the other end will hear a beep from his watch, followed by your voice and your message. If/when he (or she) replies, you’ll get an alert on your Apple Watch when the transmission arrives.
Alternately, you can open the contact card and tap the Talk button. This sends an alert to the contact. He/she can then talk to you via the app if they wish.
A cool touch: with Walkie-Talkie, you can list yourself as available or unavailable. If you don’t want to receive any messages, open the Walkie-Talkie app, scroll down, and slide the Available toggle to the off position. With Availability turned off, your Walkie-Talkie contacts can't send you any messages. When you’re ready to receive messages, slide the Available toggle to the on position.