The world may soon be blanketed in (or infested with?) bazillions of tiny computers that are “a cubic millimetre in size, come equipped with sensors to monitor temperature or movement, say, and can send data via radio waves”. That's a description of a prototype called the Michigan Micro Motes. It's the latest development in the field of “smart dust”.
Motes scavenge for their own energy needs. They can be embedded in structures like buildings and cars, or in the body. The applications are infinite. The current obstacle is communications: “For the same chunk of energy a mote could perform 100,000 operations on its CPU but only transmit one bit of information to the outside world.” This is certainly a bottleneck. On the other hand, if millions of motes lodged within the concrete of a bridge simultaneously emit a one-bit alarm that indicates a fracture, the bridge – and lives – might be saved. New Scientist