Unsafe window?

Is it possible to pull variables off of an iframed web page like the grease monkey unsafewindow for Firefox? I would like to make an addon for an HTML game by pulling variables and utilizing functions on the page. I can code it using grease monkey but I'd rather build an app using my licensed c2. Any ideas on how to go about doing it?

is this what you are looking for ?

http://www.scirra.com/forum/click-outside-the-game-screen_topic53410.html?KW=outside+game

If the iframe URL is on the same domain as the parent page and does not sandbox it, you should have full access to the parent page's variables. MDN's documentation should tell you more.