Miracast is a technology used in many modern smart TVs and TV boxes (like a roku for example). It allows you to stream your screen over WIFI. Having a button to use miracast in the system menu would be very useful.
There is already a gnome app for it called gnome network displays and it’s source code is here GNOME / gnome-network-displays · GitLab, but it’s not on https://apps.gnome.org for some reason