American Express Butterfly Card
Amex describes that The Butterfly card, "works interchangeably with your traditional American Express® Gold Card. Even though it has a different Card number, it's linked to your regular Card account with all the same benefits."
Implications - This kind of linking technology has made the American Express Butterfly Card totally a must-buy in my eyes. The simplicity and convenience that this technology brings is totally revolutionary and makes me want a Butteryfly Card right now!