Re: RF Signal Harvesters!
This has been discussed here many times.
The link you show is for harvesting power from a transmitter located very close to it. In my pocket I carry I carry an RFID tag which has no battery or other source of power. When I approach my house the gates autromatically open for me. The RFID tag is powered by harvesting energy from a transmitter mounted on the gate. Mine uses a lower frequency but the link shows a unit working at 915MHz.
What you must understand is the energy isn't 'free', you have to produce it nearby, typically within a few metres and pick some of it up to power the circuit. If you take the transmitter away and try to use radio waves present natuarally or from other man-made sources, the amount you will harvest is only a few microwatts unless you are located VERY close to a powerful radio/TV station and it will not be enough to use for a practical application like a charger.
Brian.