Check out the video above, which introduces Facialytics, a service that blends the best of facial recognition and computer analytics to track a large group of people's emotions over time. With just an infrared camera and facial rec technology, Facialytics analyzes a crowd's reactions to, say, a commercial, movie, concert or presentation. In the right industries, this information will be invaluable.
HoneyBadger is another interesting use of facial rec that created some buzz--both good and bad--at Photo Hack Day. The app uses your laptop's camera and facial recognition technology to recognize when someone is at your computer. If it determines that the user is not the laptop's registered owner, it'll send you an alert via text message. Meanwhile (and here's the contentious part), it'll run the user's image against your friend's Facebook photos in an attempt to identity him or her.
Although HoneyBadger only searches your friend's photos, it could go a step further and search all public Facebook photos. And that, in my opinion, is where things would get creepy.