Yes, double-checking like the way 'recaptha' sign up forms work! Two images re-confirmed by millions across the web. Great idea. I wonder if there are other

Yes, double-checking like the way 'recaptha' sign up forms work! Two images re-confirmed by millions across the web. Great idea. I wonder if there are other ways to confirm data in other instances... (Where recaptha-like processing is n/a).