Your husband's dream strikes me as a jokey comment about the human condition itself. Everyone, even the most astute car guys (I'd venture your hubbie thinks Tom and Ray have a hotline to The God of Small Things) has to make decisions based on incomplete information. So it's pretty funny that this gizmo only tells you after the fact; I mean, thanks a lot.
Your husband's dream perhaps reflects a longing for measurable standards in an uncertain world. "Right" is a pretty relative concept. Knowing how dreams love to monkeywrench our preconceptions, I wonder if this one isn't suggesting your husband reexamine the whole idea of "getting it right." After all, there's another connotation to the word right----righteous, honorable; the idea of "doing the right thing." How do we know when we're ethically on track? As it happens, we human beings have a pretty accurate piece of built-in equipment---our own gut. When that fails, there's also this back-up, anti-pollution device known as a conscience.