Mobile network outages can take down networks for hours, leaving us stranded without one of our most critical lines of access to the world. What good is a smartphone if it can’t phone, especially in an emergency?Earlier this year, an AT&T outage took down services for more than 12 hours in many of the most populous cities in the US. And earlier this month, a Verizon outage caused some customers to be stuck in SOS mode for a large part of the day. These outages serve as a reminder of the perils of relying only…