id Software's John Carmack has released an open source iPhone port of Wolfenstein, you can download it over here. Voodoo Extreme published the full 5,100 word document that details the development of this iPhone game. Here's a snip:
I had been frustrated for over a year with the fact that we didn't have any iPhone development projects going internally at Id. I love my iPhone, and I think the App Store is an extremely important model for the software business. Unfortunately, things have conspired against us being out early on the platform.
Robert Duffy and I spent a week early on starting to bring up the Orcs & Elves DS codebase on the iPhone, which would have been a nice project for a launch title, but it wasn't going to be a slam dunk. The iPhone graphics hardware is a more capable superset of the DS hardware (the driver overhead is far, far worse, though), but the codebase was fairly DS specific, with lots of Nintendo API calls all over the place. I got the basics drawing by converting things to OpenGL ES, but I was still on the fence as to whether the best approach to get all the picky little special effects working would be a complete GL conversion, or a DS graphics library emulation layer. Coupled with the fact that the entire user interface would need to be re-thought and re-tested, it was clear that the project would take several months of development time, and need artists and designers as well as coding work. I made the pitch that this would still be a good plan, but the idMobile team was already committed to the Wolfenstein RPG project for conventional Java and BREW mobile phones, and Anna didn't want to slip a scheduled milestone on the established, successful development directions there for a speculative iPhone project.
After thinking about the platform's capabilities a bit more, I had a plan for an aggressive, iPhone specific project that we actually started putting some internal resources on, but the programmer tasked with it didn't work out and was let go. In an odd coincidence, an outside development team came to us with a proposal for a similar project on the Wii, and we decided to have them work on the iPhone project with us instead. We should be announcing this project soon, and it is cool. It is also late, but that's software development...