I think you'll find that you don't need it in late-binding languages like Objective C, Ruby, Lisp and so on. Like Jamis' revelation that he was going down an overly complex path when he tried to build needle, a DI framework for Ruby- Net::SSH revisited.
Here are some links that will hopefully give you some sample code to do similar things in Objective C. With categories you can essentially change any class's behavior at runtime. See Mac Developer Tips – Objective-C: Categories and the Cocoa API docs on categories. Essentially you don't need some central place to ask for "the thing that does x" that is configurable, because you can just instantiate TheThingThatDoesX directly and if something else needs to change/hook into that behavior it can use categories.
