No clue on supported languages. If the UI is written in Objective C/C++ then that is going to open up some interesting possibilities, what with the language supporting Categories.
http://www.fscript.org/"Interactive introspection, manipulation and scripting of Cocoa objects."
If Objective C/C++ went deeper, say
down to AcRxObject is derived from Object or NSObject, then the runtime extensions that would be capable is mind boggling.
I know Apple tried to put the kibosh on one element of that feature in OS X 10.6, but I think injection is still easily done.