Add audio notification option to mail applet for new mail

I think it would be good if the user could select a sound to use as an audio notification of new mail arriving.
I have developed this myself already for personal use, but am not sure if my code is up to standard. I would love for someone to take a look at it.

Additionally it probably makes sense to use the gnome system sound "new email" as opposed to selecting a file in the applet preferences as my personal solution does, however I'm not sure what the "desktop agnostic" philosophy may have to say about that...

I believe this document may shed some light on how to access the gnome desktop sounds:
http://developer.gnome.org/doc/whitepapers/SystemConfig/sound.html