As electronics energy requirements decrease in some areas (like sensors) it becomes possible to power these chips in more inovative ways.
The WISP, Wireless Identification and Sensor Platform, that I mentioned before in some of my posts is progressing and some interesting results have been achieved. One for sure is in the area of using the electromagnetic field present all around us, generated by radio, television, telecommunications antennas to power sensors. http://seattle.intel-research.net/wisp/
At Intel, researchers are now able to harvest radiowave energy producing a 50 microW output, enough to power several types of sensors. To put this into perspective a pocket calulator runs on 5 microW.
A nice application of this technology is a hat, developed by a professor of the Duke University, Matt Reynolds, that embeds a sensor to detect danger in a construction site (like approaching bulldozers) and triggers the emission of a beep to alert the wearer. It is powered by the electromagnetic field created by electrical equipment in the area.
I can envisage ambient ecosystems created by hundreds of sensors (and identification tags, RFID) powered by radiowaves, thus avoiding the problems of powering, that will completely transform the way we are relating to the environment. More than that, I am using the word ecosystem because these sensors create a platform that can be used by many parties to get data and deliver services.