I wanted to spin up a hardening service back in the mid-90s, based around what we knew of Tempest. I even named it Echelon Consulting (as in "upper echelon," but with a nod to ECHELON). My spouse wouldn't let me, they felt it'd be too risky to get involved with that environment, and we were just starting our family.
But... yeah. You could tune into VGA monitors up to a mile a way using consumer hardware, and reception is perfectly legal (lots of case history to back this up)!
I figured my pitch would be to walk in with a briefcase setup, flip a switch, and show them what the receptionist was working on. Then ask if they were worried if competitors could know what they were working on (not a threat, just bringing awareness), or would they be were interested in some expensive cables/hardware.
Now that the kids are grown up and divorce pending, I've debated getting back into the netsec field. Lots of fascinating angles to be had in unexpected hardware boundaries... and my background in data science/machine learning/DSPs could prove fruitful in signals reconstruction...
