That is certainly a very useful service.<p>I think the solution need some improvement, because:<p>1. The system relies in a third party person. What happens if the user loses the qrcode? Or even if he becomes unavailable?<p>2. What if the system send the e-mail, but the user doesn't see it (mail server error, spam inbox, etc)?<p>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.<p>I hope you find solutions for these problems.<p>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.<p><a href="https://myaccount.google.com/inactive" rel="nofollow">https://myaccount.google.com/inactive</a>