Gurgle ... gurgle ... gurgle ...

That's the sound of the submarine snorkel.

But if you click on the link at the end of the article, you'll be presented with "cell signal booster" devices. Those claim: A cellular signal booster works by amplifying signal from a “donor” antenna that is usually installed outdoors, often on the roof.

So it's apparently not something like a femtocell that works over the Internet.