reCAPTCHA already does this, actually. It's part of the way Google trains their computer vision algorithms to recognize numbers. http://techcrunch.com/2012/03/

reCAPTCHA already does this, actually. It's part of the way Google trains their computer vision algorithms to recognize numbers. http://techcrunch.com/2012/03/29/google-now-using-recaptcha-to-decode-street-view-addresses/ http://techcrunch.com/2012/03/29/google-now-using-recaptcha-...