In addition to audio formats, one could also add the ability to play back videos and integrate the ability to make and respond to phone calls (using the Bluetooth API). One may want to extend the application to make it more flexible and modular, so that, for example, one could add a module that would add the voice commands and resulting actions.
Having voice output would be convenient as well, making it more aligned with the current commercial offerings. For this, one could use the text-to-speech API that's available in the Qt framework.
It would also be useful to add more information to the infotainment system by querying remote APIs for things such as the current weather, news updates, and maybe even running updates on a current football game. The voice-based UI could be used to set up timers and task reminders, integrate a calendar, and much more...
