The other little issue that he has not considered, is that most Wifi versions are DSSS. You can't even see the signal without reversing (demodulating) the spreading process - it just looks like noise. The coding gain for 802.11b (for example) is 10 odd dB. 802.11n is OFDM, but spreading the TX power across many low powered carriers is making recovering energy harder, not easier. Those little carriers are not in phase....
While recovering usable power from a non modulated single frequency RF source is hard, it might, with gain antennas, short range and careful management of losses be possible to get a little power transmitted.
Spread spectrum, 2.4 GHz, low gain transmit antennas (you can't choose that one) and all sorts of path losses, simply impossible.
There's possibly a reason that all wireless charging schemes use modulated magnetic fields.