When I registered my PLB, I set up a gmail account and included that name and the password on the registration form.
That way, when I loan the PLB to others I can send an e-mail to that gmail account and, if the PLB is activated and the rescuers cannot reach me - they will still be able to access the gmail account to get information about who is using the PLB.
Also, I sent an e-mail to the account and listed a lot of information that would not fit on the registration form - personal descriptions, vehicle descriptions, supplies carried, etc.
Oh, I used the PLBs serial number as the name for the gmail account and it is so long and unusual it hasn't yet been hit with any spam.
Just an idea.