I have long dreamt about building a portable phased array for this purpose, but additionally using the phase difference between receivers to visualize where the transmission source is.
> When I made the first video and photoshoped my impression of what I thought this would look like, I never imagined it would actually be this close. It's official, our telescope can map the wifi in a building as if it were any other form of light.
In effect a camera into the RF world!