In iOS 5 introduced in WWDC2011, there are two new things that can help Augmented Reality App. development.
1. A Direct Path for Video Data to OpenGL
There is a video background in most augmented reality applications in general. One of method to render the video background is using OpenGL texture, using glTexSubImage2D, and it has been used in many AR App. However, calling glTexSubImage2D causes delay and the overall OpenGL performance decreases.
Apple's new CVOpenGLESTextureCache let developers directly copy video data from memory to texture and it clearly improves the performance as shown in the demo (See the WWDC video of the session 414, Advances in OpenGL ES for iOS 5).
OpenGL ES programming on iOS has been handy because managing thing required for OpenGL rendering, such as timers, display links, drawing functions.. etc., were not that much convenient. In addition, EAGLView was not really integrated to CocoaTouch.
The GLKit in iOS 5 helps developers manage those things and also provides other functionalities: math functions for simple linear algebra, OpenGL texture management, and special effect with shaders. Though GLKit, developers can make their Apps more shiny and more efficiently run.