Does the Android Auto app require Android 5 on the car dashboard that it is streaming data to?
(Phone has Android 5)
Based on this tweet from Android,
Get #AndroidAuto today w/ Pioneer products & an Android 5.0+ device; now available in US, UK & AU. More partners coming soon.
So you'll need three things,
Android Auto compatible head unit.
For example, the Pioneer AVIC-8100NEX Navigation receiver head unit
An Android phone running Lollipop or higher versions.
Also, you need a compatible cable to connect the head unit to your Android smartphone.
You'll also need a compatible microUSB cable such as the Pioneer CD-MU200 cable (or a similar microUSB-to-USB cable) to connect the phone to the receiver.