Amazon teased single sign-in across apps when it launched its new 4K Fire TV last September. It's only now, though, that the company is making good on its promise. If you have a login from a cable TV provider that supports SSO authentication (like Dish, DirecTV, AT&T Uverse, Verizon FiOS and Cox Cablevision), you can sign in once and have access to a a ton of TV network apps. The new ability should roll out over the next several hours, according to an Amazon spokesperson.