I am also exploring the possibility of implementing offset mapping on the iPhone using OpenGL ES! After 2 weeks of research and experimentation, I want to say that it is almost impossible to achieve on iOS5 + devices! You can download the powerful version of PowerVR Insider SDK v3.1 Mac here: http://www.imgtec.com/powervr/insider/sdkdownloads/index.asp and try the “DisplacementMap” example (cow face) in the example folder. Hope you can understand.