In March Microsoft promised to deliver Push to Talk walkie-talkie type functionality to their Microsoft Teams app on mobile, saying:

Walkie Talkie
Walkie Talkie, a push-to-talk experience that enables clear and secure voice communication over the cloud, enables teams to communicate instantly and always stay on the same page. This native built-in app in Teams turns employee or company-owned Android smartphones and tablets into a walkie-talkie, reducing the number of devices employees must carry and lowering costs for IT. Available in GCC.

The feature was initially only available to government users but a new Microsoft 365 roadmap entry suggests it will be coming to everyone in the near future, with Microsoft saying:

Microsoft Teams: Paging on Teams phones

Like traditional walkie talkies, the Walkie Talkie app on your Teams phones provides an instant push-to-talk (PTT) communication for your team. It allows you to press and hold a button to speak to your team, and release the button to listen. Users can connect with their team using the Teams channels.

General Availability, Worldwide (Standard Multi-Tenant), Microsoft Teams Android

Release: September 2021.

The feature will send a voice message to your channel when you press the microphone in the walkie-talkie tab.

On rugged devices, companies may add a dedicated hardware button to make the feature more accessible.

Look forward to the roll-out of the feature in the next 8 weeks.

via Techradar