A story called "Smart Sensors, No Batteries" in the December 12, 2005 issue of Time recounts the story of Markus Brehler, founder and CEO of EnOcean. Brehler launched the Siemens spin-off to provide low-power wireless sensors that scavenge enough energy to allow operation without battery use. EnOcean's STM 100 sensor module, incidentally, won a 2005 Best of Sensors Expo award; it uses a small solar cell and energy store to allow several days' operation in darkness. (http://tinyurl.com/748bt)