This was recently posted by a USCG SAR coordinator to a private email list:

I was working a case the other day of a 406 EPIRB activation on a non-US vessel. After speaking to the Captain several times and unable to locate the correct EPIRB he finally found. It was attached to the Voyage Data Recorder (VDR). This was something new that I hadn’t heard of. We did receive a GPS encoded position with the EPIRB which make sense. I was wondering how common is it to have a 406 EPIRB attached to the VDR? Have you been on a vessel where they have that?