Since a while back the Walkie Talkie app in Teams is in Public Preview on Android. With an Andriod phone it is possible to start the Walkie Talkie app, connect to a channel (only one channel at the time) and then push the big button on the screen to talk to all other users connected to that same channel.
In order to set this up an admin needs to go to the Teams Admin portal, "Teams apps" and "Setup Policies" to add and pin the Walkie-Talkie app named "Walkie Talkie". This is all described in the article "Walkie Talkie app in Microsoft Teams".
If you have a Samsung Galaxy Xcover Pro it features a nice hardware button located on the side of the phone that can be mapped to the Walkie-Talkie function in Teams. When activated and logged in to a Walkie-Talkie channel you do not need start the screen and log in with a pin if this button is activated. You can simply press it, hold it and talk just as you would have done with a regular Walkie-Talkie device. To map this button to the function in Teams you have to use a Mobile Device Management (MDM) system like InTune or Samsung Knox.
For InTune please refer to the following article from Samsung: "Microsoft Intune - Key mapping for Teams"
If you do not have InTune configured for your mobile Office 365 users it is possible to use Samsung Knox which is found at the URL https://www.samsungknox.com
In Samsung Knox you have to create a login, add a (trial)license and add your device as a device to be managed by Knox. First, create a "dynamic" profile for the phone and select the Knox version to be "3.4 or above".
After going through a number of screens with setup information and choices you come to the "Device settings" page. Select "Add Configuration" under "Remap hardware keys (XCover Pro and Tab Active Pro only)" and set the "Key mapping template" to Microsoft Teams.
Finish the creation of the profile and assign the profile to the Xcover Pro phone using its "Device ID" which is the IMEI number of slot 1 as found in Settings / About Phone on the phone.
On the Xcover Pro phone itself go to Settings / About Phone / Software Information / Knox Configure and click "Apply latest profile". The phone will then connect to Knox and download the profile where you have configured the button.
Every time someone is pressing the Walkie-talkie button, either on a screen or as a hardware button on the Xcover Pro a sound is played to alert people about this. This sound can be turned off or replaced with a vibration instead, go to Settings / Walkie-Talkie in the mobile Teams client to configure this.