The Smile TV is a design by David Hedberg that requires only happy people to watch its contents. To work, viewers must smile otherwise the TV will not turn on.
Many psychologists state that the simple act of smiling will induce feelings of happiness within the person doing the grinning. Perhaps, using a few smile TVs around the country will increase the overall joy index of a place! The design uses a facial recognition system to detect whether or not someone is showing their teeth or not. If a frown becomes apparent, the TV message will become scrambled, similar to how it used to when the iconic "rabbit ears" weren't set in the exact right position.
The Smile TV will induce happiness purely from the act of sitting in front of the device.
Photo Credits: designboom, davidhedberg.info