I briefly looked into the idea of a passive receiving antenna on the nearby hilltop with a cable leading to a passive transmitting antenna located in the basement.
The problem I saw was that the FCC would probably get on my case for having re-transmitted this signal and the pager company would also be concerned because the receiving antenna would create an area of low signal strength behind the antenna, perhaps depriving other customers of the paging company from receiving their signals.
I can see a similar problem with the devices being suggested in this article. If a room full of people are soaking up the energy from a Wi-Fi there might be just that much less for the folks expecting a connection to the internet. I see much regulation ahead.
It has been garbled by the passage of time, but I can dimly remember my dad telling me about a guy who lived near an early radio station who built a contraption that converted the AM signal into heat. When he began it wasn't illegal.