No CAPTCHA reCAPTCHA: An upgrade to the existing reCAPTCHA API you currently use on your site. This new API will let your valid users directly bypass the CAPTCHA test with just a single click while providing stronger security to your site. We call this the “No CAPTCHA reCAPTCHA” experience. We expect to move all existing reCAPTCHA sites to the new API in 2015. We would like to invite you to be an early adopter of this new enhanced API before it becomes widely available.
Here is a link of a beta:
As for reCaptcha alternatives, what do you think about this one: http://random.irb.hr/signup.php