The Oolong Engine is written in C++ with some help from Objective-C. It will help you to create new games and port existing games to the iPhone and the iPod touch.

Features:

OpenGL ES 1.1 support with extension handling
Math library that supports fixed-point and floating-point calculations with an interface very similar to the D3D math library
Support for numerous texture formats including the PowerVR 2-bit, 4-bit and normal map compression formats
Support for PowerVR’s POD (Scene and Meshes) and the 3DS files formats
Touch screen support
Accelerometer support
Text rendering to support a basic UI
Timing: several functions that can replace rdstc, QueryPerformance etc.
Profiler: industry proven in-game profiler
Resources streaming system
Bullet SDK support (for 3D Physics)

http://code.google.com/p/oolongengine/