I travel internationally a lot and my parents and grandparents get calls like this on occasion. I send them an annual email reminding them that I will never call asking for money. I also give them a password in the email and let them know that if someone claims to be calling on my behalf about an emergency they will know this word (I give it to my lawyer and girlfriend plus business contacts that might actually have occasion to call in an emergency). My relatives know that if the person doesn't know the word they should hang up immediately.
I established this system because it is possible I will be involved in an accident or something and I do want my relatives to be able to trust someone calling if I am unable to do so. Many scams start with news of an accident so this usually stops them before they get to the asking for money part. I also make it explicitly clear that an emergency call would never be a request for money. I have savings and insurance and there is no occasion where I would need money from relatives, ever.
How will you never ask them for money, I was stuck in Vietnam, had my cards and cash stolen. Visa will not send a replacement to Vietnam. There was no alternative except to get my sister to wire me some money.
Then you go into an Internet cafe or borrow somebody's phone and do a video call to establish it really is you asking.
The countdown timer to when this can be convincingly deepfaked is ticking, but while a pre-recorded video is within realm of possibility (if the scammer can get access to video of the person, which is already hard), being able to fake a live conversation is still a ways off.
Also, I'd tell you to leave a backup card in a separate place from the rest of your belongings, but you've probably learned that the hard way already!
I've been traveling extensively for 10 years, over 60 countries and counting. Still haven't ever been in a situation where I needed relatives to send money. I have multiple banks, cards, credits cards, accounts and lawyers who can handle these types of issues for me.
I've also built up a network over the years so I have friends in virtually every major city on the planet. You could literally spin a roulette wheel of cities and drop me into one anywhere on the planet with nothing in my pockets and I'd be fine. People are far more helpful than you realize and of course knowing people helps.
I was completely broke once in one of the most dangerous cities on the planet (San Pedro Sula, Honduras) due to poor planning and a city wide internet outage that took out all ATMs. I also didn't speak any Spanish at the time. This was before I had multiple banks too.
In the end it wasn't really an issue at all, bus driver let me ride for free to the next town and personally escorted me to a safe ATM. Once you've been through things like that a few times you realize most situations just aren't as big a problem as you might think.
What if you get kidnapped and don't have enough money? I highly doubt there is no world in which you would ever need money. When you make blanket statements such as "X cannot ever happen" you're asking to be wrong.
A better approach would be to establish a set of preshared keywords that convey information about what's going on.
That's why they gave their parent's a password that could be used in case they ever actually need money. I remember growing up, my mom told me a password that would be used if an adult I didn't know was trying to pick me up from school or was in some way trying to get me to come with them. I think it was only used once when my mom's coworker picked me up after school because my mom was stuck at work. Nowadays, you need multiple signatures, a letter from your congressman, and a notary to let anyone that isn't the parent pick up a kid from school but this was before all of that.
Parent here: in Massachusetts, you just file a form with the school authorizing specific people to pick up your kid. Those people have to come in to the office and present their driver's license or similar. That's all the bureaucracy.
No, you can't have someone bring a form with them and show ID. Too easy to abuse.
However, you can list as many people as you like and change it at any time by visiting the school. So we have four or five neighbors listed and my sisters who live in other states.
Kidnapping is a real, albeit unlikely threat in many of the places I end up in. That's why I have lawyers and insurance. There is no scenario in which I want my grandparents or parents involved in a kidnapping situation in any capacity.
The most basic solution. People age 70+ keep paper books of hand written names and phone numbers next to their home POTS phone. Have them write down the "password" next to your name in the book.
I established this system because it is possible I will be involved in an accident or something and I do want my relatives to be able to trust someone calling if I am unable to do so. Many scams start with news of an accident so this usually stops them before they get to the asking for money part. I also make it explicitly clear that an emergency call would never be a request for money. I have savings and insurance and there is no occasion where I would need money from relatives, ever.