Hey guys.

KDE Neon has a system tray app that allows the user to pause and resume media playback using the button on a bluetooth headset.

What's this called? I'm looking to install it under another KDE distro ..

I think you mean the Media Player under Extra Items in the System Tray (right click the up arrow in the system tray, choose Configure System Tray, scroll down to Extra Items and see if Media Player is selected).