It's axiomatic in the digital world that if an app or service is free, you're the product. Or your data is. So what to make of consumers who are willing to pay handsomely for the privilege of being spied upon?
Wearable fitness devices act like the most intimate of observers, silently tracking users' heartbeat, logging every step taken, every calorie burned, your hours asleep - and report the data back to their masters. Consumers love them.