Nope I've been looking into making one myself using javascript where it will change theme without having to press a button.
If you made one I'd definitely use it (If it were released as a plug-in I mean). :/
Sorry to get your hope's Ooka up but I can promise you I will not release one, I've been looking at Ryan's theme changer trying to undertand how it works and still don't have a clue.
Your best asking in request to someone more capable.
I am looking into this as well, the theme changer plugin seems to be working via a form interface.
So if you can plug in the right id in the right URL scheme, it should work, theoretically.