This phrase is created by a man none other than Mr. Mac. It has a similar meaning to when a pitch in baseball is so perfect you knock it out of the park. It can take on many meanings but it is most commonly used to describe a situation or a good looking girl.
It can also go by it's abbreviated use or rimwh, or rimfwh for added effect. Use your imagination on the F.
That Pia from American Idol is right in my wheel house.