EnOcean Wireless Sensors Don't Need Batteries (Video)
'The EnOcean technology is an energy harvesting wireless technology used primarily in building automation systems; but is also applied to other applications in industry, transportation, logistics and smart homes,' says Wikipedia. There's also a Siemans spinoff company called EnOcean, and today's video is an interview with its president, Jim O'Callaghan. But EnOcean technology is the real star here. The idea is that energy-efficient sensors can be powered by energy harvesting, i.e. drawing energy from their surroundings, including such low-level sources as light, temperature changes, and pressure, which can be the pressure of your finger on a switch or even changes in barometric pressure. The EnOcean Alliance has a professionally-produced video that describes their technology and notes that self-powered wireless sensors not only save energy but save miles of wire between sensor nodes and controllers, which means it's possible to install more sensors sensing more parameters than in the past. (Alternate Video Link)
ITYM Siemens
If you had actually bothered to watch the video, or read the transcript, you'd know that EnOcean is not using RF harvesting to power any of their devices. They are using mechanical, solar, and thermoelectric energy harvesting techniques to power ultra-low power sensors, and to generate RF signals to control other powered appliances (e.g. desk lamps). They are using clever engineering, but they are not making any claims that violate the laws of physics.
iFind was a scam. There was no way that a device that size could harvest, store, and utilize RF energy at the levels claimed by them. Not to mention that the so-called "inventor", supposedly with multiple advanced degrees in engineering and medicine, had absolutely no presence or history on the web.
And Slashdot didn't "kill" iFind. Kickstarter killed it, after performing a little due diligence and realizing that something was fishy with WeTag. But if Slashdot helped pushed Kickstarter into checking into the background of WeTag's principals, then so much the better.
Energy harvesting from ambient RF does work, but to capture significant amounts of energy requires lots of area (e.g. an antenna or large pickup coil), or to have RF energy beamed directly at the device. At no time does EnOcean claim to be using RF harvesting to power their devices; they are only using ultra-low power RF radio bursts for short-range communication.