This is an experimental implementation of Wi-Fi Display (aka Miracast).

The application will stream the selected monitor if the mutter screencast
portal is available. If it is unavailable, a fallback to X11 based frame
grabbing will happen. As such, it should work fine in almost all setups.

To get audio streaming, you need to change the audio output in pulseaudio
to use the created "Network-Displays" sink.