There is an interesting looking python library on Github for accessing BBC Sounds. It might well be a good starting point for anyone considering producing a plugin.
Btw, does sounds work for folks not in the UK as well? I recall that you needed a proxy for the old iplayer stuff, has that changed recently?
I think that you can download most podcasts & listen to live streams. Some podcasts & all programme downloads (catch-up stuff) are geo restricted for legal rights reasons, so you would need a proxy or alternative in such cases.