At the recent Rawcon Conference in San Diego, Intel Research Seattle staff member and UW CSE affiliate professor Joshua Smith described the scavenging of 60 microwatts of RF power from a TV tower 4.1 kilometers distant. The power was used to drive a thermometer/hygrometer and its LCD display. The approach harvested enough energy to drive many Wireless Identification and Sensing Platform (WISP) applications. A WISP is essentially an RF identification (RFID) tag with a microcontroller on it, according to Smith. He says the increase in integration and decline in power consumption of digital circuitry has led to improved functionality per microwatt of scavenged energy. “The range at which you can power a device [with a given amount of ambient RF energy] should double every four years,” he says. Power-harvesting could lead to a perpetual sensing platform that does not need batteries.