There are a variety of special things that happen when you enter a “duress password”. Google shows 4 among the first 6 entries. I just thought of another.
I don’t know what all hooks there are to trace financial transactions but imagine a duress password for online banking. It would produce no immediate visible difference in output to the user but would trigger a trace that would cause any substantial proceeds of any initiated transaction to be traced, as well as an alarm to police. I would guess that this would provide a substantially greater chance of unwinding the transaction and in fact identifying the miscreants than what I imagine is in place now.
Even the rumor of such a mechanism in place would deter some nefarious activities.
Perhaps someone should start a rumor.