Does teaching perfect pitch help in foreign language aquisition?
I believe that perfect pitch (or absolute pitch) is not so essential in foreign language acquisition, because being able to name and differentiate a particular pitch does not help.
If anything, what is more important is relative pitch, because what's useful in being able to learn a language (and its accent) is being able to hear the difference in pitch from one syllable to another. This ability helps the most when you are learning to SPEAK a foreign language, and I suppose helpful somewhat in UNDERSTANDING too, especially if it's a language like Chinese where the relative tones are crucial. (that's why I always tell foreigners learning Chinese to try to 'sing' the words.)
I think it won't make much difference in learning to write or expanding your foreign language vocabulary.
Basically, being musically-inclined and having a 'good ear' will be a great help in being able to speak a language well.