I don't know what the screen is made of...but MOST devices like Cell-Phones, Tablet devices...use Gorilla Glass. It was developed by Owens Corning in the 60's. Then sat around for some product that could benefit from it. Most LCD screens glass is made of Gorilla Glass these days.
http://en.wikipedia.org/wiki/Gorilla_Glass
Gorilla is extremely difficult to scratch.
Screen protectors for cells or tablets is different. It's mainly used for fingerprint...or the whole device is put in a case to protect the device from dropping/water. I really don't see the need for a screen protector for a screen in your car. It's NOT being removed from you pocket 30-40 times a day. It's NOT being dropped a couple times a week.
If it gives you piece of mind...go for it. It's not very expensive. But I really don't think it's needed.