Get the Whitepaper called iSpy: Automatic Reconstruction of Typed Input from Compromising Reflections. The authors investigate the implications of the ubiquity of personal mobile devices and reveal new techniques for compromising the privacy of users typing on virtual keyboards.
You can download it from the following link: https://packetstormsecurity.com/files/download/106678/CCS2011.pdf
Source: https://packetstormsecurity.com/files/106678/iSpy-Using-Reflections-To-Spy-On-iPhones.html