Sensors have a bundle of worldchanging applications, but one of the big hang-ups so far has been designing batteries with a reasonable working life. That design concern may be addressed, at least in urban environments:

[W]ithout a persistent power source, such sensors would need their batteries replaced every few months. In other words, ubiquitous sensors could also mean "ubiquitous dead batteries," says Josh Smith, a researcher at Intel Research in Seattle.

Smith and his team are addressing this problem not by working on longer-lasting batteries but by trying to eliminate the need for batteries altogether. Instead, their prototype devices employ the same power-scavenging technique used by battery-free radio frequency identification (RFID) tags.