Pixel and Nexus phones have gained Android Auto Wireless support as Google has officially confirmed that a number of the devices in those device lineups will now be able to connect to Android Auto in the vehicle without having to plug the phone in using the compatible USB cable. This is good news for anyone that has been wanting to use Android Auto in the car but didn't want to deal with plugging in the device, though there is still some initial "plugging in" that will need to be done during the setup process, as noted by Google in the instructions to configure everything on the Google Product Forums where the announcement was made.
Although Android Auto Wireless does now work with a handful of smartphones there are still a few caveats to pay attention to if you're hoping to get things going. The first and most obvious as Google lists this particular requirement on the Android Auto help page, and as mentioned above, is that the phone you're using has to be a Pixel or Nexus phone. More specifically it needs to be either the Pixel, Pixel XL, Pixel 2, Pixel 2 XL, Nexus 5X, or Nexus 6P. Beyond that, there are only select aftermarket head units which support Android Auto Wireless, and at the moment these are only coming from two brands - JVC and Kenwood.
Another restriction is that you need to have a car that supports Android Auto Wireless, and the downside with this is that Google does not list which cars currently support this feature. So even if you have a car that supports Android Auto, it may not support the wireless version of it, and there doesn't seem to be an easy and convenient way to figure that out. If you're planning to give things a go and you have a compatible device, and think you might have a compatible vehicle or head unit, you will also need your device to be running at least Android 8.0 Oreo and have a "high-quality" USB cable for the initial setup. Lastly, the Android Auto app has to be at leasy version 3.1 or higher.