There surprisingly isn't that many out there, and the ones I've seen are windows based (yuck). You're much better off making one yourself like you're mentioning, its what I did. I used curl to post to about 120 different torrent sites automagickly for me. What used to take me several hours, is now a simple 1 line command, and I walk away

Oh yes, torrentflux w/ mass uploader helps a lot too