I remember hearing about a study on very simple electronic voting machines. These machines had a bunch of buttons representing the candidates. And in the study, they were able to make a decent guess of who voted what by looking at the rf emissions from the machine from a distance.

I could imagine a whole computer being there could make the rf emissions less predictable. I can definitely think of some ways of making a simple machine like that more resistant against an attack like that. Idk if the study looked into that, I can't find the study anywhere.