In my RubyCocoa projects I just creat an objective C class that  
contains wrapper functions around any c functions that I need. As it  
is objective c, rubycocoa knows how to bridge automagically.
Thanks!  I tried it two ways:
1. Wrapping it in obj-C
2. Writing a C extension that opens the OSX module and inserts the method

The C way seemed a little easier/more straight-forward even with gluing manually (about 9 non-comment lines):
#include "ruby.h"
#include <Carbon/Carbon.h>

// CGSSymbolicHotKey is adopted from work by Joe Ranieri, Alacatia Labs.
extern CGError CGSSetSymbolicHotKeyEnabled (int hot_key, bool is_enabled);

// Function will be mapped as a class method on the OSX module
static VALUE t_set_symbolic_hot_key_enabled(VALUE self, VALUE hot_key_code, VALUE is_enabled)
/* Ruby objects must be converted for use in C.  Bools are probably okay, but I'm tired, lol*/
CGError result = CGSSetSymbolicHotKeyEnabled(NUM2INT(hot_key_code), is_enabled == Qtrue);
return (VALUE) INT2FIX(result);

/* Every extension defines a global Init_* function
 * which is called when the interpreter loads it
void Init_symbolic_hot_keys() {
  mOSX = rb_define_module("OSX");

  // Define a module function, the C function it maps to, which takes 2 arguments (not counting self)
  rb_define_module_function(mOSX, "CGSSetSymbolicHotKeyEnabled", t_set_symbolic_hot_key_enabled, 2);

Sean DeNigris