The latest development version of the Software application (the graphical tool for searching and installing new applications in Fedora) now has support for browsing and installing add-ons.
Basically, this feature has the ability to list any additional packages in the Fedora Repositories that will add additional functionality to the application, and let the user install them.
In a recent post to his blog, GNOME developer Kalev Lember talks about the new feature:
The screenshot above is for Audacious that was the very first application in Fedora Rawhide to start shipping addon metadata. If you are an upstream author or a package maintainer and want your addon to show up in GNOME Software, it’s pretty easy to do. All that is needed is to drop a small file in /usr/share/appdata/ with the metadata and it shows up.
This new feature is already in the development release of GNOME (3.13), so it is likely that this new feature will be available in Fedora 21.