Let’s get this out of the way up front: Apple Watch is not a watch. It may well be, as Apple CEO Tim Cook says, “the most advanced timepiece ever created.” But “watch” is a misnomer, a branding sleight of hand.

The Apple Watch is not a watch in the same way that the iPhone was not a phone — or at least not what we knew to be a phone at the time. “Watch” is not the device’s primary functionality, just as “phone” was not the iPhone’s primary functionality. iPhone was an honest-to-god computer in your pocket — and Apple Watch is an honest-to-god iPhone on your wrist.

But there’s a big caveat: It’s an iPhone on your wrist that requires yet another iPhone in your pocket.

Onstage at Monday’s event, Cook touted Apple Watch as “the most personal device Apple’s ever created” — a line he also used at the September 2014 event when the device was first uncrated. But Monday, he repeatedly described Apple Watch as “a rich and integral part of your life.”

Vintage Apple hyperbole, to be sure, but it speaks to the company’s vision of the device, which — in a conga line of use cases — was shown paying for groceries, checking sports scores, calling an Uber, checking in for a flight, opening the door to a hotel room, and remotely opening a garage door for a daughter who’d lost her house key.

But to be all these things, to serve all these purposes, Apple Watch needs an iPhone.

In fact, it’s largely pointless to buy an Apple Watch if you don’t already own an iPhone or intend to. Tentpole functionalities like payment and authentication are iPhone-dependent. In order to pay for your groceries by simply raising your wrist near your grocer’s payment system, you must first pair an Apple Watch with an Apple Pay-enabled iPhone via Touch ID fingerprint authentication.

And, unless I’m misunderstanding Apple’s messaging, more basic functionalities are iPhone-dependent as well. In order to browse Apple Watch apps and download them, you must do so on an iPhone. Setting up notifications requires an iPhone as well. As Cook said, “Apple Watch has been designed to work with iPhone.”

If the Apple Watch does all that it promises to, it may well become as indispensable as the smartphone is today, setting Apple up to define another massive shift in computing.

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