This question led to a new package:
autonum
I know that cleveref is not compatible with showonlyrefs as it says in the cleveref manual. But I have a book-length document that depends on showonlyrefs and I would like to start using cref without having to go back and add a \notag to each of the equations that I do not want to assign a number to.
Is there a known hack or an easy way to use cref? I have recently begun to appreciate the power of cleveref and would like to use it without going back and changing each and every one of my equations.