Many thanks to SWLing Post reader, Richard Cuff who has apprised me of the goTenna: a small device that allows you to use your smartphone to send and receive messages and share your GPS location with others without the need of mobile phone service.
goTenna describes their device:
“goTenna is a small, rugged device designed to make “No Service” no problem. Just pair your smartphone with a goTenna and communicate off-grid with those near you who also have goTenna, anywhere on the planet, regardless of access to cell reception or wi-fi. goTenna allows you to send and receive texts and share GPS locations on beautiful offline maps, without ever relying on central connectivity. Depend on it in all kinds of situations: when hiking in remote areas, traveling, attending music or sporting events or during an emergency. Plus, because goTenna is end-to-end encrypted, it’s not just for when you’re off-grid, but when you want to be.”
Some sources claim the goTenna is based on “short-wave” radio frequencies; I discovered that it operates between 150-154 MHz, so this is not the case. Still, it would be fascinating the see the potential in a device that could use the HF spectrum to create a smart phone mesh network. Though the antenna would need to be longer, communication distances in rural areas could surpass that of VHF frequencies. In the end, text messages would be an ideal format for such a system.