Password Validator validates password_hash generated passwords, rehashes passwords as necessary, and will upgrade legacy passwords.
Jeremy also has an introductory blog post: PHP Password Hashing: A Dead Simple Implementation
The really big deal here is the ease of upgrading from your current legacy hashes to the new, more secure PHP password hash hashes.
This is good stuff. Hopefully everyone starts to move to the more secure passwords instead of the old md5 + salt that was so popular back in the day.