1. A wireless end-user device, comprising: a wireless wide area network (WWAN) modem to communicate data for Internet service activities between the device and at least one home WWAN, when configured for and connected to the at least one home WWAN, and between the device and at least one roaming WWAN, when configured for and connected to the at least one roaming WWAN; and one or more processors configured to apply a WWAN differential traffic control policy so as to disallow background Internet data service provided using the WWAN modem and the at least one roaming WWAN, but allow background Internet data service provided using the WWAN modem and the at least one home WWAN, and indicate to a particular application, via an application program interface (API), one or more network access conditions based on the applied WWAN differential traffic control policy and the particular application operating in a background mode, wherein the one or more network access conditions include a network access condition that indicates the unavailability to the particular application of an Internet data service that is currently available via the WWAN modem and a roaming WWAN to a different application, but that is indicated as unavailable to the particular application.