Satellite-powered phones are often clunky, expensive, and, well, dependent on satellite connection. GoTenna wants to bring off-the-grid text and GPS communication to your smartphone. No cell service? No Wi-Fi? No problem. The Brooklyn-based startup today announced funding of $7.5 million, led by Union Square Ventures.

GoTenna’s USB key-type device works using Bluetooth low-energy (LE), a version of Bluetooth that was built for the Internet of Things (IoT). Users can pair the device with the GoTenna app on a smartphone, which needs to be within a range of 20 to 30 feet. The phone sends the message to the device, which then transmits it over long-range radio waves to other GoTenna devices. “All of this happens in a matter of milliseconds,” wrote GoTenna cofounder and CEO Daniela Perdomo, in an email to VentureBeat.

Perdomo founded GoTenna with her brother in 2012, just after Hurricane Sandy. “Everyone from regular people to public safety personnel was disconnected due to a failure of central infrastructure,” she wrote. “From there, we thought up GoTenna in our search to figure out how everyone’s regular phones could enable communication, no matter what.”

Their first device, GoTenna, is sold in pairs for $149 across the U.S., and can be found at Amazon and REI, among other retailers. The device works on a two-way radio range and is mainly used for outdoor activities. Last September, the founders announced GoTenna Mesh, which allows users to extend the range of connectivity anywhere in the world. Currently in preorder, the device is sold in pairs for $179 and will start shipping to 49 countries late this spring.

GoTenna does not charge a monthly subscription fee, but users can choose to upgrade to GoTenna Plus for $10 per year. Additional features include detailed topographic maps, trip statistics, and automated location tracking among trusted contacts.

GoTenna claims to have several tens of thousands of customers to date. Most are consumers, but, according to the founders, early adopters also included public safety personnel, groups within the U.S. Department of Defense, and humanitarian response NGOs. To better appeal to this customer population, the company launched a third model last month, the GoTenna Pro.

The military-grade mesh-networking radio works on a range of licensed spectrums in ultra high frequency (UHF) and very high frequency (VHF), and will ship later this year. It costs $499, about 30 to 40 times less than comparable professional mesh-capable radios, according to Perdomo.

In addition to being lighter and cheaper than other military-grade devices, Perdomo claims GoTenna is easy to use, “with its intuitive smartphone integration.”  “Operationalization is immediate, no special training is required as it works just like any other messaging app on your smartphone,” Perdomo wrote.

Existing investors Walden Venture Capital, MentorTech Ventures, Bloomberg Beta, BBG Ventures, and Collaborative Fund joined Union Square Ventures in today’s round. The new money will be used to support manufacturing and delivery of the new devices, as well as to expand the team of 23 people.

GoTenna has raised $17 million in venture capital to date and received several grants from the likes of Google and the U.S. Department of Defense.

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