Apple Watch's Walkie-Talkie feature in watchOS 5 uses FaceTime Audio technology
The Walkie-Talkie feature of watchOS 5 that enables push-to-talk conversations between Apple Watch users is effectively a FaceTime Audio call rather than recorded audio clips being sent between wearable devices, a design decision that helps keep the function secure by not retaining any recorded messages.
Shown for the first time during the WWDC 2018 keynote, Walkie-Talkie allows users to communicate with contacts using their Apple Watch. Pressing an onscreen "Talk" button opens the line of communication between the two users, with the recipient's device automatically playing out their contact's message over speakerphone.
Described as "real-time voice but with the spontaneity of short messaging" during the demonstration, the process of setting up the Walkie-Talkie communication and how it operates reveals that it works similar to a limited-functionality FaceTime call.
To establish the session, the user needs to select a contact they want to use Walkie-Talkie with, prompting a request on the recipient's Apple Watch asking to start a conversation. Once accepted, the connection is made, and users can communicate via the push-to-talk system.
When the Talk button is pressed by one user, the call is opened up for just their side, immediately transmitting the live audio to the other person's Apple Watch. The recipient will be alerted to the incoming communication with a notification sound and haptic feedback, before playing the live feed aloud.
A prototype version of the feature shown at WWDC took between five and ten seconds to initiate the initial Walkie-Talkie session, but the push-to-talk communications happen almost instantly, in both directions. The initial delay is when the "call" connects between the devices, which can take place over cellular and a Wi-Fi connection.
While the call stays active even when both users are silent, there will be a limit to how long it will remain open. The initial timeout for the session is currently set at five minutes without activity, but Apple is reportedly still figuring out the appropriate duration for the feature.
By using a live call, Apple avoids the privacy implications of another method to create push-to-talk messaging, namely recording voice memos on one device then transmitting the file over to the recipient. As a live call, none of the communications are recorded by the app, and therefore there is no audio files to acquire.
In its current state, Walkie-Talkie communications will automatically be established and audibly play on a user's Apple Watch once they have accepted their contact's request, allowing for the call to be reestablished in the future in the same way. Aside from turning the Apple Watch off, the user can also turn off incoming Walkie-Talkie calls with an availability toggle.
It is unclear if Apple will make changes to the availability options before watchOS 5 is made available to the public. Also not clear is when the feature will make it to the beta releases of watchOS leading up to the full release.
Apple has already provided the first developer beta of watchOS 5, which is expected to be made available to the public this fall as a free update for Apple Watch Series 1 and later devices. Original Apple Watch owners are not expected to be able to use watchOS 5.