I can even tell you how it starts.
"Baz!" Elena called. "What is this funny little thing you have in this jar?". The answer echoed down the corridor. "I call it a Babelfish. It's really amazing. If you stick it in your ear, you can understand a Lairouiban, a Cetagandan, even Miles at his worst. Actually, I recommend you take it out if he starts talking, because it's a terrible beauty to understand what he's thinking. But I just thought of another use..." Baz trailed off.
(A scene later)
"Baz, that was wonderful. It seems like any sound I made, you knew exactly what I wanted..."