Tesla was interested in this, eh? I did this sort of thing in 1967 when I put a capacitor on the output of my crystal set, and was able to (very weakly) light a standard panel lamp. Nothing is new, only the details change.....
Unwarranted grumpiness. Harvesting power from radio transmisssion is indeed not new.
What they demonstrate, however, is transmission from the 'receiver' to additional devices by modulating how much power is absorbed or reflected.
This is fundamentally different from just using the harvested power to run a second transmitter, because modulating backscatter is 'orders of magnitude' more efficient.
http://en.wikipedia.org/wiki/Crystal_radio (no battery needed for wireless reception)
Using that concept to also produce transmissions is the kicker here.
Now, "the walls have ears" takes on an entirely new meaning in "The Internet of Things"...