1. A method comprising: displaying, on a user interface of a controller of a media playback system, a zone identifier that identifies a zone of the media playback system, wherein the zone comprises a playback device that has audio-playback software installed thereon; and displaying, on the user interface of the controller, an application identifier in association with the zone identifier, wherein the application identifier indicates that a software application installed on the playback device is configured to operate as an add-on software component to the audio-playback software.