display a menu bar icon on osx

An implementation of this may be found at:

http://the.taoofmac.com/space/blog/2007/04/22/1745

The API for displaying icons in the OS X menubar is called NSStatusItem. It's going to be difficult or impossible to use from a wxPython application, though -- you will probably have to write your application using PyObjC to use it effectively.