I’ve been saying for a few years now that once we reach a saturation point with wireless internet access, cafes and other establishments will start advertising the absence of wi-fi in the same way the currently advertise its availability. Even an always-online geek like myself sometimes feels the urge to retreat from the cloud, after all, even if only so I can sit down in peace with a book for an hour or two.

But there are plenty of other reasons why you might want to spend time somewhere that wi-fi can’t reach you… or alternatively somewhere where there’s wi-fi available which can only be accessed by someone inside the building or room in question. The classical way to make a room impermeable to high-frequency signals is a Faraday cage, but that’s neither cheap or architecturally simple. Now there’s a much simpler option which may aid the proliferation of wi-fi cold-spots in urban areas – a special paint based on an aluminium-iron oxide that resonates in the same frequency range used by wi-fi routers.

And not just cold-spots. I can definitely see a market for wi-fi hot-boxes – rooms with carefully controlled physical access (think burly doormen and surly cashiers) wherein you and a bunch of, er, associates can set up an ad-hoc LAN connected to the web through a heavily encrypted router. No one outside that room – even the establishment’s proprietors – could know what data had been passed around within it.

If you’ll excuse me, I’m off to book a one-way ticket to Mexico City and draw up a business proposal…