There was an alien eyeball in every room, and it was always watching people. The alien eyeball(s) never interfere, just always watching people.
I remember this alien eyeball idea as a side description in a bigger story. Alien eyeballs were not the main plot. Also, I remember it like these aliens provide free buildings for people, in exchange for having an always watching eyeball in each room. For whatever reason, I picture the idea as an organic eyeball with organic vines on the walls.
I think I read it somewhere in a way bigger story, like e.g. Dune, or The Foundation, but I'm not sure, maybe it was just a small SF novel. I remember reading it from a paper book, long time ago (before Google).
Does anybody remember the title/author for this, please? Already googled a lot, but couldn't find it.