But it's a new emerging industry. It's super easy and cheap now to put sensors, gyroscopes, compasses, small bluetooth / wireless devices on stuff and build apps to monitor all sorts of things.
For example, Nike+ wristbands are simple wearable tech to monitor your running. You can take that same concept, and expand it to all sorts of things to help modify and track your behavior while integrating seamlessly with your body. One company I investigated was creating simple sensors you could stick onto toothbrushes that monitor how many revolutions and how long your child brushed their teeth, and then synched to a cartoon app on the iPhone that scored the child and gave them little prizes when they did well.