Now, we know some of the technological facts that are driving this change in our lifestyle — the uptake and diffusion of mobile devices, the exponential improvement in data storage and data processing, and the remarkable improvement in human biometric sensors. This little black dot there is a 3D accelerometer. It tracks your movement through space. It is, as you can see, very small and also very cheap. They're now down to well under a dollar a piece, and they're going into all kinds of devices. But what's interesting is the incredible detailed information that you can get from just one sensor like this. This kind of sensor is in the hit biometric device — among early adopters at the moment — the Fitbit. This tracks your activity and also your sleep. It has just that sensor in it.