OK, I'll keep this for reference. I've talked to one of our developers and he thinks this should all be doable with the zimlets. He sees three components:
1) activating the zimlet based on some message properties
2) building the zimlet and accessing the microphone and speaker
3) sending the mail
Believe it or not, he said part three would be the easiest! ;)
If we ever get around to doing this, I'll be sure to post.
Thanks again for all your help.