Anyone who has been to a festival will know it’s a struggle to contact anyone using your phone.

With tens or hundreds of thousands of people trying to send texts or make calls, local networks are quickly flooded and become all but useless.

New York startup goTenna thinks it has the solution for situations like this: a small radio device that syncs with your phone and lets you send encrypted messages to other goTenna users within range.

The founders, siblings Daniela and Jorge Perdomo, are already taking pre-orders for the product on Shopify. GoTenna is the latest in a string of startup businesses that are now accepting bitcoin payments through the e-commerce platform.

“The tech-savvy bitcoin demographic is a perfect target consumer for goTenna because bitcoiners quickly understand goTenna's technology and appreciate our commitment to privacy and decentralisation,” explained Daniela Perdomo via email.

Not that the technology is necessarily all that hard to understand. Each goTenna device pairs with a smartphone via Bluetooth. Then, through goTenna’s app, you can send text messages, or your location, to a specific device or to all goTenna devices within range.

However, instead of relying on phone networks, goTenna customers can send messages peer-to-peer. The service is designed to be private and secure, something that is central to both founders' beliefs, says Perdomo.

He continued: "GoTenna is a communication device and it comes at a critical time when both tech companies and government agencies prove over and over again they don't care about consumers' privacy."

The devices use the 151-154 MHz radio band, a low-capacity frequency range that allows for relatively long-distance transmission. At ground level each device would be limited by the horizon (around three miles), though technically it could broadcast as far as 50 miles in ideal conditions.

The devices cost $149.99 for a pre-order pair (one goTenna device alone wouldn’t be very useful) but will retail at $299.99. They have three days of battery life “on average use”.

The company claims that the device can be used anywhere in the world, which is technically true, though it may not be legal in certain jurisdictions. In the UK, for example, the 151-154 MHz radio band is licensed.

“Frequency use is regulated around the world and different for each country, and consumers should certainly check local laws. However, goTenna's technology does actually work anywhere in the world,” says Perdomo.

Although Shopify recently allowed merchants to choose BitPay or Coinbase for bitcoin payments – previously only BitPay was available – Perdomo has “been happy with BitPay so far”.

Perdomo added that “bitcoin isn't just some trend we're jumping on, [my brother] was a very early-adopter of the tech.”

She claimed that Jorge knew about the illicit online marketplace Silk Road early on, and that “if he hadn't used so many BTC to buy our youngest brother a fake ID back in 2012 before bitcoin blew up, he might be really wealthy right now. The knife-twist is that the fake ID was confiscated after only a few months of use.”

GoTenna’s devices are due to begin shipping “in late fall this year” but the batch is limited to US customers and is yet to receive FCC approval, though Perdomo says they are confident their devices will clear any regulatory hurdles.

Disclaimer: CoinDesk founder Shakil Khan is an investor in BitPay.