Zap -- Sit Up!

No longer does your mother have to shout, "Sit up!" Now your shirt will.

The Posture Sensing Shirt "alerts you of improper posture to help prevent neck, back, and shoulder pain," according to the advertisement. "Whenever you slouch, an electronic sensor detects the increased tension in the shirt's built-in microfilaments and vibrates to let you know your posture is not optimal (vibration ceases when you correct yourself)."

Sounds something akin to the Invisible Fence.