It's interesting. You go to a maser pointed at people's heads. I go to magniplanar listening devices.
The Great Seal Bug was 3' across back in '45. They never did figure out all the gack in the US Embassy in Moscow. What I know is that if you type in "planar microwave emitter array" into Google Images you see a bunch of SEM graphs.
Imagine this: you've got some passive surveillance devices that are acoustic cavities that modulate when excited by microwave energy. You've got them tuned such that you can literally stick them into the wall like a thumbtack and have a listening device in a room. Only problem is, the gain is dependent on a bunch of correct collimation: your microwave emitter has to be just so. Your bug has to be just so. And if you're FSB, you're probably good at this.
But if you're Cuba, you jack the shit out of your emitter gain.
And people's brains start to cook.