The closest approximation we have for such a device is a computer with spyware on it– a computer that, if you do the wrong thing, can intercede and say, “I can’t let you do that, Dave.”
Such a a computer runs programs designed to be hidden from the owner of the device, and which the owner can’t override or kill. In other words: DRM. Digital Rights Managment.
These computers are a bad idea for two significant reasons. First, they won’t solve problems. Breaking DRM isn’t hard for bad guys. The copyright wars’ lesson is that DRM is always broken with near-immediacy.
DRM only works if the “I can’t let you do that, Dave” program stays a secret. Once the most sophisticated attackers in the world liberate that secret, it will be available to everyone else, too.
Second, DRM has inherently weak security, which thereby makes overall security weaker.
Certainty about what software is on your computer is fundamental to good computer security, and you can’t know if your computer’s software is secure unless you know what software it is running.