The Happiness Hat is a wearable device that detects if you're smiling and provides pain feedback if you're not. An enclosed bend sensor attaches to the cheek and measures smile size, a servo motor moves a metal spike into the head inversely proportional to the degree of smile. Through repeated use of this conditioning device you can train your brain to smile all the time. This is the first in a series of Tools for Improved Social-Interacting.

http://www.lauren-mccarthy.com/happinesshat (less info)