Apple CEO Tim Cook. Getty/Chris Hondros Apple is working on a pair of Google Glass-style smart glasses powered by your iPhone, Bloomberg reports.

And it's no surprise why: Apple CEO Tim Cook has said augmented reality, the technology used to project computer-generated imagery onto your field of vision, is "a big idea like the smartphone."

What Cook won't say, however, is how Apple's move to AR is a defensive move to preserve the supremacy of the iPhone, its most important product, for another decade.

In a recent interview with Business Insider, Microsoft technical fellow Alex Kipman, the chief inventor of Microsoft's pioneering HoloLens "hologram" goggles, said he saw augmented reality as replacing the need for a smartphone.

After all, if your text messages, photos, and phone calls are projected onto what you see, why use a separate device?

Now Apple has to figure out a way to make sure the iPhone stays relevant in that world. Meanwhile, its biggest competitors are preparing for an all-out assault on the concept of the smartphone itself.

Self-contained

Companies like Microsoft and Facebook are working hard to accelerate the demise of the smartphone and the rise of AR, attempting to sidestep the iPhone's dominance entirely.

Importantly, Microsoft's HoloLens is a self-contained device, not requiring a connection to a PC or phone to function. That's a big deal for Microsoft, which has almost no presence in the smartphone market. It means that if the HoloLens takes off, Microsoft owns the whole thing.

Similarly, companies like Facebook's Oculus and the mysterious Magic Leap are trying to build standalone augmented-reality and virtual-reality devices. The opportunity is tremendous — if they can capture that market, it wouldn't matter that they don't have smartphone operating systems because they'd own the next big thing.

And Google is more committed to the Android operating system than to the traditional concept of a smartphone. The original Google Glass didn't need a phone to function, and it seems unlikely that the long-rumored Google Glass 2.0 would need one either. As long as whatever next-generation glasses come out run on Android, Google's strategy is satisfied.

Microsoft's HoloLens is self-contained, requiring no PC or smartphone to function. Microsoft HoloLens

All of this is an existential threat to Apple. Removing the need for a smartphone would demolish the market for the iPhone, the product Apple's strategy hinges on. We're years away from AR truly being mainstream, but the foundation is being laid.

Now the burden is on Apple to get there first. If it can build an AR headset that depends on the iPhone to function, it can keep its all-important phone business alive for a long time. In Apple's ideal world, the iPhone sits at the center of the AR market.

But if Apple fails, Microsoft, Google, Magic Leap, and Facebook are circling, ready to take advantage.