We are using an AT&T "unlocked" aircard for just that purpose. It has to be unlocked or it will not go to another network. We use AT&T because it is GSM, but you may want to use a CDMA card (Verizon). If you're in the US you may have to pick a network like AT&T or Verizon and go with one of the aircards for their network and let the aircard work as a WiFi antenna when you have Wifi near by. We use a Verizon devise when in the US.