As far as I know, that little piece above the speaker is the proximity sensor, and it's location hasn't changed between the 3 models (someone correct me if I am wrong) I am speaking of the iPhone 4, The Verizon iPhone 4 and the iPhone 4s.
The White model of any of these phones shows the proximity sensor because it cannot work through the white paint, but it is in the same place as the black phones. Any iPhone 4 screen protector should work fine.
I started using screen protectors for my iPhone 4 because I have a couple slight scratches on my phone. I have had some HUGE scratched on the screen protector- and I still don't know what caused them. But I can throw the screen protector away and put a new one on.