(Video Link)
Lauren McCarthy created the Happiness Hat - a gadget that detects whether or not you're smiling. If you're not, it drives a small metal spike into the back of your head to encourage to you resolve that problem quickly:
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. The device runs on Arduino.
Link via Geekologie
UPDATE 10/29: The YouTube video's status was switched to private, so I swapped it out for a Vimeo version.
Reminds me of the ab control device that was making its rounds a few years back. It had a sensor that could tell when you wern't sucking your stomach in and would sound an alarm.
I wouldn't be suprised if nobody here has heard of it... it probably wasn't a big seller after people got fed up and tossed the thing off.
If grimace=smile.
Now if we don't smile, we get a metal spike in the back of the head.
I'm really hoping Lauren McCarthy is making a statement about how society expects women to be welcoming, congenial, and friendly.
Bugger that for tuppence.
Seriously, this is <obviously] an art piece; a commentary on how we're all expected to be happy and congenial due to a common marketplace mentality. Well played.