I'm working on a desktop application for OS X using Ruby-Tk, and I would like to provide an Apple Events interface for the application. This means that the application would define a dictionary of AppleScript commands that it would respond to (corresponding to Apple Events being sent to the application), and users/other applications could script the Ruby-Tk application with AppleScript commands. Other scripting languages support such functionality--Python through the py-aemreceive library at http://appscript.svn.sourceforge.net/viewvc/appscript/py-aemreceive/ and Tcl through the tclAE library at http://tclae.sourceforge.net/. I've been looking for similar functionality in Ruby and have come up empty.
One possible mechanism is the rubyobjc bridge, which provides a low-level interface between Ruby and Objective-C, but this gem appears to be little-used and is sorely lacking in examples and documentation, so I am not sure if this would be a fruitful path to pursue.
NB: MacRuby might work but it is not compatible with Tk, so that rules out MacRuby. Also, RubyOSA and rb-appscript are not what I am looking for--they allow Ruby to send Apple Events to other applications, not receive them.