I had a thought about the Babel Fish from the Hitchhiker's Guide to the Galaxy the other day. My understanding (which doesn't quite match the Wikipedia description) is that it feeds off brainwaves of others and translates them for you. It would, therefore, allow you to understand inarticulate people as well as foreign languages. Someone who is unable to get their thoughts out into words would still be understood. However, I don't think it would work for television the way it is mentioned in passing in one of the books. It would need real people, not just sounds.
Mokalus of Borg
PS - It's possible that Wikipedia has it right and I'm wrong, though.
PPS - Wouldn't be the first time.