Sonnet is a device that promises to be the world's most advanced mobile mesh network, letting you exchange messages, photos, voice messages and GPS locations without the need to access a cellular or internet network extending to a range of up to 15km between two devices if there is line-of-sight.
The Sonnet essentially transforms your phone into a more advanced walkie-talkie, equipped with water-resistant material and can be used as a charge for your phone. The idea is to give lovers of hiking a familiar way of communicating at locations with no cellular network at their disposal, removing your smartphones' dependency on any network or cellular infrastructure.
Sonnet is currently in the midst of their Indiegogo campaign. The current price for backers is $89 USD + shipping (comes with 2 devices) and is estimated to ship in December 2017 for backers.