Andrew do it so that it sends the 6 digit code to the mobile device for confirmation just as the banks and credit cards account  verifications are all doing today. That’s the best bet but you may or may not want to include something pertaining to the location of the device but also it needs to receive email in addition just to have on record of the action taking place so that if it was done by a hacker or third party or anything else that’s not the actual user then there is a link included in the email to be able to select and file a report just as a security measure. This will male users feel secure and protected which will give more credit and higher rankings to your company and others sites upon reviews by the public and critics.

I also am curious about if UNA will offer the option to allow a site to get an https instead of just http and also have option to SSL for their sites to enhance security measures and more protection so trusted sites can show certification proof to the users and reviewers. This was a big thing and it held true when I used it when hosting through the  Network Solutions servers.