[mcswell]

Fiction... indeed, science fiction. There was a short story (I believe in Analog) in the 1960s about this, later amplified by the author into a book.

But getting to your real point, about the use of an MMU safety monitor: I'm sure this works. But I confess, the first thing I thought about when I read that was Cloudstrike's explanation of their pre-release testing mechanism: running "validation checks" on the content, rather than running the actual software. Had they actually run their release, they would surely have detected the bug, since it apparently bricked every single Windows machine that downloaded it.