TkXext "has the ability to send events to any window, embed windows in Tk, and send events to embedded or non-embedded windows." Unlike Android, it doesn't yet (as of September 2001) have capabilities for dispinfo or event recording.
GPS maintains TkXext at http://www.xmission.com/~georgeps/tkxext/ , with the help of several others.
TkXext is X-based; it's available only for Unix.
(more accurately, it's available as source, and good luck figuring out how to compile it under windows to work with Exceed [L1 ] or Reflections/X... But if you do work it out, by all means let George know about it.)