[MacRuby-devel] Is this possible in MacRuby?

Hi All, Is it possible to make a Lion app(/option) with MacRuby which allows you to change the opacity (alpha value) of other apps/windows via the View menu? So say I have a PDF open in Preview, I'd go to: view menu > transparency, and then set it to 50% Is this possible? Would it be a pain to do? I don't think I've seen any MacRuby apps that add functionality to other apps like this so am guessing it's not trivial. Cheers, Aston