Action follows T-Mobile's rollover move in December
Also announces Passport smartphone with rounded corners for AT&T
Fashion is a big driver, as is battery life, and more functions
New tech allows smartphone users to find others in low-power mode for games or collaboration apps
Beta has enhancements for adding caller ID, enabling more devices
Carrier also opens up Digital Life home security and automation to third parties
Worker productivity and apps to better engage customers are on the horizon
10 of the top 17 smartphone manufacturers now come from China
Bezos says 'stay tuned' for future iterations
The offer could be a boost for consumers but a big risk for Sprint, which had shaky revenues in the last quarter
