I have a buddy who put one of these on the nav screen in his SL550. If you've ever seen a nav screen that's been 'touched' for more than a couple years, you know that they tend to develop non-removable 'smudges' on the spots where you touch the screen frequently.

I just ordered one for my P-car. I'll post a report on it once I receive it.

http://www.navprotector.com/screen-protector-vehicle-navigation.html

 

Interesting. I look forward to your report.