A sense of things to come

Sensors can keep a remote eye on almost anything

THE military uses for wireless technology are persuasive. For example, pilots can fly above a war zone and drop thousands of small wireless sensors, the size of a small pebble and costing a dollar apiece, over the terrain. As soon as they settle the devices start communicating with each other, weaving themselves into a dense digital mesh. They pick up vibration and sound, so they can identify advancing troops. The sensors can also detect the presence of nuclear, chemical or biological agents. The information they pick up is relayed to a satellite. For power, they "scavenge" energy from the environment, using solar energy or temperature changes.

The Economist April 28, 2007