Word is that pretty much all aircraft will required to have ADS-B as of 2020. I don't pretend to know a whole lot about it, but I understand it's supposed to work like a GPS and a Transponder (although, unless they change the rule between now and then, transponders will still be required). However, I've seen some forms of GPS (like the Stratus Ipad, for instance) that are said to be ADS-B equipped. If a pilot carries a handheld GPS with ADS-B, would this qualify if the aircraft itself were not ADS-B certified?