Oolong is a game engine based on OpenGL ES on iPhone.
It provides many useful things for developer, such as math library, touch screen support, accelerometer support, and text rendering. It can be integrated with the Bullet SDK, a physics library) for physics simulation.
It also support sound using OpenAL.
Are you curious about the origin of the name Oolong ? It is the name of a famous Chinese tea.
More information is here : Oolong Engine