Google's car platform, Android Auto, gets updates just like the rest of Android. The company is now letting users try out beta updates to the system, delivered via the Android Auto app on the Play Store. The beta version should run on any car stereo that's Android Auto-capable.
Google is predictably using the Play Store beta system to distribute the new app. If you're new to this distribution method, just go to this opt-in link, click "Become a tester," and the Android Auto app on your phone will be automatically updated to the beta version. When there is one, anyway: Google isn't promising that it will always be running beta features, as Auto development is a little more pokey than some other first-party apps.
Indeed, that seems to be the case now: the Android Auto Beta listing is currently showing the same changelog as the standard version from July 9th, beginning with an improved Do Not Disturb functionality. There have been a few more variants released since then (which we've tracked on APK Mirror), but no huge user-facing changes.
Though Google is announcing the Android Auto app beta today, it's been running since at least May, according to our uploads. It looks like the company wants a much wider pool of users with which to test tweaks and features. So get to it.