It didn't seem to exist, so I went ahead and wrote one today:
It's an awful hack written in Ruby using dozens of unreadable regexes, but it works. It absolutely does not produce compilable code, but it converts a ton of stuff including method declarations, initializers, message-sends and variable declarations. I haven't started using it in earnest yet, but it should drastically cut down the time needed to port code.
Feel free to publicize this on your Twatters and Reedits and whatever other new-fangled BBSs you kids use nowadays!
--Jens