[Communitivity]

I wonder if this will cause an interest in in Faraday Cage walls: outer wall sheetrock with a copper wire mesh support, with a ground to prevent re-radiating. You'd also need to have the same mesh on the house roof and attic walls. Copper would be best for conductivity. The mesh holes would need to no greater than 5mm to block 2.4Ghz and 5Ghz. This is rounded down to the nearest mm from the equation:

   hole size (m) = speed (m/s) x frequency (Hz) 
   (.0599 = 299,792,458 * 5,000,000,000)

The better the conductivity of the metal the thinner the thickness can be. It's differences between 10s of microns though, so in practical terms thin copper fire should work. Even thin steel wire should work.

Your biggest leakage problem would be doors and windows. Window screens sized to stop mosquitos (1.2mm hole size) will help with this, for the windows. Metal screen doors should help.

This won't prevent all leakage, but should prevent most of it.

[danw1979]

Leakage doesn’t seem to be the problem that is being explained here: it’s internal sensing within the home by existing wifi devices.

[Communitivity]

It doesn't need to be your wifi devices, it could be your neighbor's, if you're in a townhouse or your house is close enough.

But I agree with another commenter: if they've hacked your wifi router then you have bigger problems, as they've likely hacked all your devices then.