On my cell {and other family cells} we have our home phone number under "home" instead of a someones name.
and my parents number is under "mom & dad"

one time I found a cell in a store and looked at the contact names and one said Dad's house - so i called it from the phone and was able to let them know that I found the phone and where they could pick it up at the store.

But the ICE is a good idea then the rescue personnel could just look for ICE and the numbers would come up.