Since you're using wxPython, you've given my a plumb
> opportunity to repeat what is in danger of becoming my
> litany:
> You should check out Matt Newville's MPlot package and
> my wxmpl module, both of which exist to simply embedding
> matplotlib in wxPython applications. Both of them provide
> user interaction bells and whistles, including crosshairs
> around the mouse position.
Perhaps a wiki entry on using mpl with wx would be helpful.
http://www.scipy.org/wikis/topical_software/MatplotlibCookbook
JDH