I'm a brazilian, and on our big cities we have a type of crime known as flash kidnap ("sequestro relâmpago" in portuguese), which is a crime that consists in one kidnapper taking a hostage and cruising around with him (probably on the hostage's own car) and forcing the victim to release his banking account numbers so money can be drawn from his banking account.

This type of crime is basically a problem that was induced by the introduction of a technology (bank credit cards). But this technology could be made safer by the introduction of an emergency number. This number would work just as the normal one, so there is plausible deniability for the victim, so money could be drawn and all, but if ever used it would raise alarms on the credit central, and the authorities could be immediately called. Since close to 100% of the ATM machines have cameras around them, and there is the location of the drawn, it would be easy to check where criminals are.

For example:

Bob uses a banking card and has 2 passwords (pass A and pass B). Bob uses pass A on his day-to-day, without a hassle. Some day Eve kidnaps Bob, and forces him do release his card and a password. Bob releases pass B. Eve uses Bob's card with pass B without a problem, but doing so warns Alice that there is an emergency happening with Bob (possibly a kidnap). Alice warns the authorities.

I'm not interested in making money at all with this idea, but I would like to see it implemented, so it perhaps could save some property and lifes, so I'm asking for some directions as to what the heck I should do with it, and also some criticism.

This idea is registered under CC Attribution-Noncommercial 2.5 Brazil