Hooking into IPhone Phone application

Question

How to hook the native apps in IPhone? I'm trying to hook a MS plugin into several IPhone native apps like Calendar, Maps, Phone and etc.

For example, I'm trying to hook into the "MobilePhone.app" of IPhone. I dump all the class headers of "MobilePhone.app" and placed them in the "/user/include/MobilePhone". And in my MS plug in,

  #include <MobilePhone/RecentViewController.h>
  .............
  ...................

in the initialize method,

  extern void TestInitialize()
  {
       Class _$rcntViewCtrl = objc_getClass("RecentViewController");
       if(_$rcntViewCtrl == nil)
       {
           NSLog(@"RecentViewController is nil");
       }
       ............
  }

When I placed my dylib in the "DynamicLibrary", I always get the log message as "RecentViewController is nil". I just wonder how the "Cyntact" (from Saurik) is hooked with MobilePhone.app. Am I missing anything?

Thanks in advance.