How do you feel? Your phone may soon tell you

A variety of projects unveiled in the past year aim to give mobile apps the ability to instantly detect a person's emotional state.

A startup called Affectiva, which emerged out of MIT's Media Lab, last month launched a software developer kit (SDK) for its emotion-tracking technology. The company claims that it's possible to assess the effect that advertising and branding have on a person if you analyze that person's facial expressions through the camera of a mobile device.

Affectiva's Affdex SDK could enable emotion-tracking to be built into mobile apps. For now, the SDK supports app development on Apple's iOS.