When I first saw the thread, I thought, "Hmm, could be interesting." Then I saw it was by Vorpal Tribble and thought "Oh, it will be interesting."
Next, I noticed the name, and it made me think of Death. And his granddaughter, Susan.
Anyway, awesome feat. I think the necessity to listen to them for three minutes negates the otherwise unlimited use, but doesn't make it entirely useless.
Question: Would scrying work? If you can hear someone you scry on? Of course, if you have access to that, there's surely other options, but it's a question anyway.
Annnnd on another note: Is there a Vorpal Tribble fanclub? I'd rescind my membership in another just to join that one.