Deep in the most endangered part of the Amazon, repurposed smartphones hang from tall trees.
Powered by solar panels, they are monitoring for sounds of unwelcome visitors - loggers. A fifth of the world's largest rainforest has been destroyed to make way for farmland since 1970.
Somewhere in the US, an activist presses a button. An electronic message pings across the world and touches down at an office in Dublin suburb Ballsbridge.
The message is processed and pinged back, finding its way to one of the phones hidden under the Amazon's leafy canopy. The phone receives a $20 top up, paid for by the US sender.
The Amazonian undergrowth rustles with the sound of approaching loggers and the phone's sensors pick it up. Now topped up, it sends an automated text message alerting local authorities. The loggers are stopped in their tracks.
The silent player in the initiative is Dublin entrepreneur Mark Roden.
His company, Ding, allows users to top up pay-as-you-go mobile phones anywhere in the world via text or website. Deforestation group Rainforest Connection is one of the more unusual customers using the service to keep its Amazonian phones in credit.
Another, the Massachusetts-based Haiti Projects, uses Ding to top-up Haitian phones owned by women working at a sewing co-operative. The top-ups are sent as a personal reward to the 100 women but also allow them to keep regular contact with customers. Ding is on track for double-digit growth next year, Roden told the Sunday Independent.
The nine-year-old company took in revenue of €25m last year and a profit of €4m.
It has built up a base of customers around the world with a website in two languages, English and Spanish and is now rolling out versions of the site in another 10 languages including Hindu and French.
Many of the top-ups it processes are small amounts, just a couple of dollars or euro. People who have migrated from the developing world to find work use Ding as a way to send money home easily.
Roden has no plans to sell or even fundraise in the near future, he said. "We have a very small fraction of the global remittance market which runs to hundreds of billions every year. There is huge room for growth."
It is looking at potential acquisitions abroad, having just bought Cuban top-up website RecargasaCuba.com.