Setting up an Apple TV in Your Home is easy. It's a matter of plugging the HDMI into the back of the ATV and the other end into the HDMI input on the back of the television set.
In the car, most Radio head units don't come with an HDMI inputs. You may see a composite RCA output so you can hook up rear screens for your passengers to view Media.
Some radios, have HDMI inputs but usually they are locked Down and give you a watered Down experience using the manufacturers Apps proxied buy your mobile Devices operating system. just like Apples Carplay or pioneer's AppRadio
If your car's Head unit has a DVD Player you may be able to watch a movie in the front seat as long is your car isn't the park position
All of the above mentioned are in place to Keep you safe so you're not distracted. Makes sense don't it
What if you want the full experience our mobile devices give us. What if you want the the experience you get in your home, like with the new Apple TV 4?
The Apple TV 4 is a great media streaming box to using your car for many reasons. It has a ever expanding app store, not only for media but for games.
The Siri Remote, unlike the previous ATV remotes is Bluetooth. You now don't have to worry about line of sight so you can install the Apple TV anywhere in the car. The glove box, the trunk under the seat etc.
Air play now works without the need to have a router in your car providing you have a fairly new device running IOS 8 or better. Apple calls it peer to peer
You can also save a large movie, TV and Music Collection on the Apple TVs hard drive using the
"One Video" ATV app seen in my video here: . Storing the actual movie on the Apple TVs hard drive is great if you don't have an Internet connection in your car.
Restrictions, the lack of inputs, and the power supply are three of the hurdles stopping most from connecting any sort of secondary Device to your cars Radio display
In the video below you can see my setup and find out what works and what doesn't work
One last thing to mention is that I use this set up to entertain the passengers in the rear not so I can watch while I'm driving. You may want to also.