goTenna

Like a modern day walkie-talkie but without the old fashioned handheld unit, goTenna links to your phone and creates an off-grid network (no NSA listening in here) capable of communicating to other goTenna-linked devices even when cell networks are overloaded, offline, or out of range. Each goTenna features a Bluetooth LE data interface, antenna, and 2-way radio, all wrapped up in a water-resistant, dust-tight enclosure that straps to a backpack or slips into a pocket. It’s totally free to use after purchase, boasts end-to-end RSA-1024 encryption, and works with both Android and iOS devices. Expect a couple miles of range in a congested city and far more in open areas, especially when elevated.

Learn more at goTenna – $150