SpaceX’s Elon Musk and T-Mobile’s Mike Sievert announced the “technology alliance” at the space company’s Starbase in Texas.

“It’s a lot like putting a cellular tower in the sky, just a lot harder,” said Sievert. “Your phone doesn’t really know it’s connecting for space. It’ll think it’s connected to a cell tower, because that phone is using industry standard technology communication protocols and it has the spectrum already built in, as the vast majority of phones in circulation today do.”

Though both executives emphasized the “profundity” of the announcement, it isn’t exactly without precedent. In fact this is exactly what Lynk demonstrated last year with its still-operational test satellite — the startup plans to provide emergency messaging and alerts across the globe from a small constellation. (“Having Elon validate this as a service is great. It’s a huge need, a huge market and a huge validation,” Lynk founder Charles Miller told me after the announcement. He also pointed out that they have patents and an FCC license, so we’ll see how that goes.)

Admittedly Starlink does have a larger presence in orbit, allowing it to — theoretically — provide more frequent and high-bandwidth connection.

But theoretically is the word, because it seems that this connectivity has not yet been demonstrated in orbit. (At least they did not say that it had been — I have contacted T-Mobile to find out more and will update if I hear back.)

“We need to do more than reprogram the satellite; we’re making a special antenna, the most advanced phased array antennas in the world. They have to pick up a very quiet signal from your cell phone,” said Musk at the event. “There’s quite a bit of complex hardware and software, because it is moving so fast — they’re traveling overhead at 17,000 miles per hour. Normally a cell phone tower does not travel at 17,000 miles per hour.”

At first the service will only enable text messages, and possibly messaging apps, though Sievert warned that “we haven’t actually begun working with other companies… it’s a bit of a technical problem that we need help from the partner with.” There would probably also be a considerable delay of “half an hour or so” until the message is sent or received.

Musk suggested, however, that the spec of the antenna and service potentially could enable multiple voice calls and real-time messaging in time.

The service will work with T-Mobile’s own licensed spectrum only for now, meaning this is something of an exclusive. However, both Sievert and Musk indicated they would like to find arrangements with providers in other countries using compatible spectrum, proffering a “reciprocal roaming” deal. That’s to be determined too.

The product and service itself is still being hammered out, Sievert noted repeatedly, but you can expect to hear more in the coming months as the details occur to the companies in question and the tech itself gets demonstrated.