Use case:
- Email a checksum link to a user asking them to update their profile data.
- When that user clicks the checksum link, request that they fill out a couple of verification fields such as postcode/date of birth/account number before being shown their data (just in case its not them).
I saw this demo'd at CiviCon London 2014 but can't remember who presented it, what it was called or if it was already part of CiviCRM or an extension. Googling for it has been unsuccessful.