zodttd ported Doom to iPhone and iPod Touch.

Quote:

Doom on the iPhone and iPod Touch, while still a work in progress, is shaping up well. It supports the retail/commercial WAD (game data) files for Doom 1 and Doom 2, assuming you provide them. Constructive feedback is greatly welcome.

More detailed instructions and videos of it in action coming soon! Meanwhile, hop on Cydia and grab the “Doom” package in the “Games” section!

http://www.zodttd.com/boards/blog/zodttd/index.php?showentry=12