Saw this on a Ted talk a while ago with the creator. He explains how they work and some possible applications.

Thats a shame. Justin Bieber, I expected so much more out of you!

@tedknaz: How are drug rehab and adult education classes any less expensive than jail? Rehab has to pay the doctors that work there, and adult education requires teachers and textbooks and computer access and god knows what else. The guy committed a crime. Its probably not his first. He deserves to go to jail.