Sniffing keystrokes from thin air

This kind of research is like catnip for infosec professionals: a study about deducing keyboard strokes by monitoring electromagnetic radiation. It reminds me that it's long been known that you can "listen" to conversations inside a building by pointing a laser rangefinder at nearby windows, and picking up the window flexes which act just like a speaker. Presumably the same technique be used to "listen" to keyboard strokes of people writing documents and emailing within a building...