The new media features are now available for Google Play Books, Google Play Music, iHeartRadio, Pocket Casts, and Spotify, with more supported apps coming soon. The idea, obviously, is to allow you to choose music or audiobooks to listen to quickly, minimizing the time you're messing with Android Auto's interface with your eyes off the road.
Along with the new media browsing interface and messaging preview Google have also announced improved search features and group messaging capabilities. So far, iHeartRadio, Spotify, Google Play Music, Android Messages, Hangouts and WhatsApp already take advantage of it, and more are assuredly on the way. On top of that, the Google Assistant's integration has been improved so that you can be a little bit vaguer in your song requests. Specifically, Google says that Android Auto can now be configured to show message previews while your vehicle is stopped, but reassures that you can turn toggle this feature off for times when you want to keep those messages private. If that's not enough, voice searches can now return a list of all the matching media results.
The text preview feature only works in Hangouts and WhatsApp right now, but is a welcomed addition to everyone who has been frustrated by only getting messages in audio form even when the auto is stopped. It should be noted that this is optional and users will need to enable it in Settings. Perhaps most importantly, Android Auto will also be gaining support for apps that use MMS and RCS, which is definitely an exciting addition.
Google Assistant always had a presence in Android Auto. And Google says that it's working to bring new updates to more music and media apps.
This update will be rolling out "in the next several days", so it should hit a head unit near you soon.