Google is moving to unify app development for Android Auto and Android Automotive. It feels long overdue, as there's no good reason to have two different routes for creating apps for what is essentially the same form factor.
Not too long ago, Google introduced a Cars App Library as part of Jetpack for EV charging and parking apps for Android Auto, and it's now making this package available for Android Automotive, too. The company is working with "Early Access Partners" in order to bring a slew of these kinds of apps to Android Automotive. You can expect applications from Parkwhiz, Plugshare, Sygic, Chargepoint, Flitsmeister, Spothero, and others.
The company plans to expand to more app categories in the future, so you might not have to wait long until your favorite services are available both on your phone and on your car. Developers interested in working with Google are encouraged to sign up for the Early Access Program using this form, or they can get more information here.