Hand held wireless devices often have diverse communication interfaces that can be used simultaneously, such as expensive (energy and dollars) long-range cellular data interfaces (3G/4G) and inexpensive short-range interfaces (WiFi/Bluetooth). In order to reduce cellular data costs, we design a content streaming system in which the cellular interface is used for communication with a server, while the short-range interface is used for device-to-device (D2D) communication. We show how D2D communication can significantly reduce the 3G/4G costs for the system while all users can still achieve a good quality of service. Using the idea of mean field equilibrium (MFE), we then design an incentive framework wherein selfish users are motivated to share content with each other.