When it comes to feelings and facial expressions, many of us can associate a certain color with the mood. For instance, we typically associate blue with sadness(as in, "feeling blue"), red with anger, and green with jealousy. What if you could use these color associations to tell others to leave you alone?
Vittorio Cuclo built a Mood Lamp that does just that out of an RGB Ikea lamp and an Arduino Duemilanove microcontroller. Vittorio's project works by mapping your facial expressions to a number of markers via a webcam, matches it to a color, and then displays it on the lamp. Essentially, you're communicating your emotional state to the room through the lamp.
The system uses the OpenCV programming toolkit for the required image processing and facial-expression recognition, and it will even look for details such as the position of your chin or eyebrows.
The project looks more at the non-verbal communication between man and machine. And it's not just a fun use of technology; it could turn out to be legitimately useful For example, I can see how something like this could be useful to those with autism, who often have a hard time picking up on others' facial expressions or other non-verbal cues.