The idea has been around for a while. If an alleged spy claimed to be deaf, the intelligence agency would use this to tell if they were lying. The person's own voice would be fed back into headphones, and deaf people are the only ones unaffected. The idea of making it into a STFU gun is brilliant.
I can attest to this WORKING. My raid leader in WoW and I were on a podcast that had a half-second delay. It completely fucked us up for the entire segment.
The first thing I thought of when I read about this device was Ventrilo harassment.