In a similar vein, I'd love to try a code review tool that's smart enough to recognize that I've moved a function from location A to location B, and can show me diffs for that function against its last known state in its previous location, and ideally would keep track of changes at the function level, rather than (or in addition to?) the file level.
Not sure how feasible that is to implement transparently though. Seems to me at minimum it'd have to require developers to add some kind of annotation to the function to include a globally unique identifier (though I'd honestly be willing to put up with that in exchange for the benefits).