It is called as magic screen which is privacy protection film for iphone.
When attached to the LCD screen of iphone, the magic screen allows functions to be performed in public place without the concern for information to be viewed by other people. The optical polarization filter allows the screen to be viewed from the front but not from a side angle of more than 30 degrees.
The magic screen is a simple and practical method of maintaining personal privacy and security for mobile devices such as ATMs, PDAs, PSP, Computers, Laptops and Mobile phones.