You can also say "Heaven knows what you were up to!" - meaning God may know, but I surely don't (and it was probably something bad).
As Jura says, anybody can be suspicious of anybody else, depending on the circumstances.
Of course, if it's a highly jealous wife and she's really angry, she may mention something that implies that the husband will soon be able to sing high notes that he wasn't able to reach before. Think of the Vienna Boys Choir.