Emergence of international data plans
It was only a matter of time before better international data plans started emerging. AT&T has a new one for unlimited iPhone/SmartPhone data in many places. This is important because otherwise NESP applications might unwittingly transfer large amounts of data when someone travels. On some phones you can detect and prevent transfer when someone is out of the country, but even better is to have data plans where the NESP program can continue sending data and receiving surveys no matter where the phone user goes. They are expensive now, but perhaps will be more affordable down the road.
http://www.wireless.att.com/businesscenter/popup/dataconnect-comp-table.jsp