Vi keys in Xcode
Here's another plugin which I made a few weeks ago.http://programming.jugglershu.net/softwares/xvim.html
This is currently developed for personal (my) use. So you may feel bad with some lack of implementation. Give me a feed back(feature request) then. I'll add some keybinds if I have enough time.
The closest you'll get is http://www.corsofamily.net/jcorso/vi/, or configuring an external editor. This has been a long-standing deficiency with XCode. (If you ask any vi user that is..)
OSX and XCode in general favors Emacs key bindings.
More info on general key-binding strategy for OSX: http://hints.macworld.com/article.php?story=20060317045211408