Actually wireless power transmission is possible; people have been working on it since the 60s. It's just so inefficient that it's no practical use.

Jane Q, you've got some good points but it's still a bit mixed up. IAAME (I am a microwave engineer)

1/ A rectenna the size of New Mexico would actually be very inefficient. Narrow beams are the best way to efficiently transmit microwave signals.

2/ Correct, microwaves are not ionising radiation. Microwaves just heat you up and cook you from the inside out, they don't cause mutations and cancer like the other sort of radiation.

3/ Correct, 100 mW from the transmitter is not necessarily 50 mW at the target.... unless the target is close enough of course :) But microwave propagation follows an inverse square law, so double the separation and exposure drops to one fourth.

4/ Radiation from cellphones and from WiFi are both in the microwave bands. Low bands, sure, but definitely microwaves.

5/ 50 mW might sound big but it's nothing. Check out Microwaves101 for more about exposure levels: http://microwaves101.com/encyclopedia/biological.cfm

For what it's worth, I think this SPSS is a crock. Too expensive, maintenance sucks, and there are too many other options that are lower risk and lower cost.