At its I/O conference today, Google announced that Android Auto is going to be available to a lot more people this year. How? You're not going to need a car or third-party head unit that supports it anymore.
An update to the Android Auto phone app coming later this year will enable the full Android Auto experience right on the phone itself, without needing to be plugged into a compatible car. The idea is that you could snap your phone into a dash-mounted cradle of some sort — which many of us do already — and just load up the Android Auto app for navigation and infotainment rather than relying on an in-dash display. (This is particularly practical now that many phones have huge displays themselves.) Like the in-dash Android Auto experience, the on-phone UI is simplified and voice-centric, keeping driver distraction to a minimum.
Of course, you'd probably still want to route audio into the car so you can hear music and navigation instructions, so a car that supports Bluetooth streaming or at least has a 3.5mm aux in jack would be preferred. But theoretically, you could just rely entirely on the phone for sound, too.
Support for systems like Android Auto and CarPlay is growing in the auto industry with each passing model year, but some manufacturers are still slow on the uptake — Toyota, for instance — so this might make the decision to buy a Prius just a little easier. If you're into the Prius, that is.