I thought about a similar service quite a few times. The problem ensuring longevity. In short, the hard part is the technical side, it's the org side.
Awesome!, Free, Opensource and does not store any data, can't ask for more
I like the idea itself. However I would not use such kind of service since I'm always assuming that when I'm dead those services aren't there anymore.
That is certainly a very useful service.
I think the solution need some improvement, because:
1. The system relies in a third party person. What happens if the user loses the qrcode? Or even if he becomes unavailable?
2. What if the system send the e-mail, but the user doesn't see it (mail server error, spam inbox, etc)?
3. What if the server/domain goes down? This type of service must the the most reliable possible. Maybe a government funded project could address this.
I hope you find solutions for these problems.
Since you touched this subject, Google has a service that aims the same, but the validation is different. If the user doesn't access his account after n months, a phone call is made to the user AND an e-mail is sent to someone the user choose.
https://myaccount.google.com/inactive