Oolong Engine is an iPad / iPhone / iPod touch Engine
code.google.com
code.google.com
All the major game engines on the platform have support for
* 3d audio
* physics of some kind
* networking
* touch input
* accelerometer apis
Many of them have their own languages (Unity), UI subsystems, and require you to architecture everything in ridiculous ways that are non-standard on the platform.
As somebody coming from a "normal software" iOS development background, this presents me with a huge learning curve to get up-to-speed on these things. I already know how to do touch events and accelerometer handling. Apple is introducing kickass APIs for game networking and such. All I want is to draw pretty 3D things to the screen and occasionally animate them; maybe some basic collision detection.
Also, the point of having yet another accelerometer/input suite is platform compatability .. these engines aren't very useful if they restrict you to a single platform, so they go for as many platforms as possible .. well all of these platforms have to have a common input method, and thats why the engines have to account for it - so that a developer can target the Engine, not the Platform, and benefit from having all these other target architectures available to them ..
Disclaimer: I've built my own 3D engine for use on Android/iPhone/Plaszma/Linux-AngstromOE environments ..
Just be thankful the trend isn't burrito flavors.