To keep it short, I guess you could say goTennas turn smartphones into really powerful walkie-talkies. Except more like walkie-texties. The self-contained signal generators require no cell towers, WiFi connectivity, or satellites to give their connected phones the power of text and GPS location sharing when off-grid, at crowded events, or during emergencies. goTenna works even when its paired devices are in Airplane Mode and, with its end-to-end encryption, can also be used to maintain privacy when signals are available.
Like walkie-talkies, all parties communicating via goTenna must be carrying the device. Usage range varies depending on the terrain and elevation, but is generally solid from 1 to 6 miles, with a theoretical maximum of 50 miles in ideal conditions. To use a goTenna, users must first pair it with their Android or iOS smartphones (via Bluetooth-LE) and then use the goTenna app to type out texts or share a location. Transmission is possible to a single person, multiple parties, or to all goTenna users within range. Once the "Send" button is hit, the data travels to the goTenna, which then shoots out long-range VHF radio waves to the intended recipients' goTennas and, finally, to their goTenna apps.
goTenna must be within around 20' of the connected phone to receive and transmit, and supports text messages of up to 160 characters. When a GPS location is shared, it appears on detailed offline maps on the recipients' goTenna app. Voice and images are not currently included in the transmission system.
At printing, goTennas were available for pre-order at a reduced introductory price, with shipment expected in Summer 2015. The signal generators are sold in twos, and each pair also includes 2 micro-USB charging cables. More questions? Check out goTenna's extensive FAQ page and you'll likely find your answer.