Just don't call it radio. Vital Alert's new wireless tech uses Very Low Frequency (VLF) to penetrate earth, skyscrapers, subways and ocean with two-way digital text and voice communication. Their Emergency Broadcast Network (EBN -- dang we're good) has now been licensed by Los Alamos National Laboratory for use by emergency personnel in urban centers and underground mining. Beyond communicating with victims and rescue teams, the tech allows for location tracking, and obviously avoids the signal pitfalls of normal GPS and radio systems. Apparently the "fail-safe" tech is also relatively cheap to implement, and should be coming soon to an emergency near you.