Starting a process in a Wayland session for data capture

[mmarkd9 at libero.it]

Hi, I'm trying to understand what does it mean for a process to be 'started in a Wayland session'. My goal would be to capture screen data for an entire desktop session (either KDE or GNOME). I know that compositors like mutter provide internal d-bus interfaces to get this kind of data and enable RDP operations (https://github.com/GNOME/mutter/blob/master/src/org.gnome.Mutter.RemoteDesktop.xml), anyway I'm wondering how would one go in order to launch a process able to use these interfaces.
 
This paragraph https://wiki.gnome.org/Initiatives/Wayland/SessionStart says
 
> Starting session services
> For starting services, there are various alternatives: D-Bus activation, systemd user services, xdg autostart files. Autostart files and systemd services can have conditions that control their activation.
 
Using a .desktop file to enable the xdg autostart seems pretty easy, but I don't understand the other two methods (i.e. systemd services and D-Bus activation).

Are these Wayland officially defined ways of starting a user process in a Wayland session (or are they gnome-specific)?
In any case what's the correct way to start a user process in a Wayland session so that it has permissions to grab screen data?