What makes watch tick?

How has no-one cracked that joke already?

I've been thinking about the watch and it's interaction and dependence on iOS devices or Computers for connectivity and data. The keynote event contained a huge amount of broad-brush information about the watch, which even the hands-on event reporting failed to add much depth to. One likely reason for this is the state of completion of the software and possibly hardware. With a launch date of 'Early 2015', Apple are being characteristically nebulous as to when we can buy it. 

Reading the runes

However there were several interesting pieces of information provided which, when looked at together, along with some already disclosed information from WWDC 2014, point in a certain direction. Let's start with the watches connection to other devices.

The pertinent information here was provided by Tim Cook  and Kevin Lynch. 

  • Tim:  the watch will require a connection to an iPhone.
  • Kevin:  you can control media playback on an iPhone or a 'computer running iTunes'.
  • Tim:  the watch can connect with: iPhone 6, 6 Plus, 5S, 5C and 5.

This indicates a wireless connection of some sort between the watch and other devices. This would also require some characteristics for this connection and strongly indicate some others.

  • Support for multiple connections.
  • Support connection without an infrastructure
  • Require low power drain
  • Support for streaming data
  • Provide a discovery mechanism

You might be looking at that list and already mulling over the most likely candidate. I venture to guess you're thinking about our friend Bluetooth™. If you're even slightly nerdy you're likely a step beyond that and thinking Bluetooth™ 4 (aka Bluetooth™ LE).
It was my first thought too. And I think we're dead wrong.
Let me explain why.


Is there any other technology that covers all these abilities? Yes.
Does Apple have existing API implementations of it? Yes.
Does it match more closely with the information provided on stage? Yes.

iOS has a high level API, which I'm a vocal fan of, that provides Nearby Networking connectivity between iOS devices. It powers the AirDrop functionality, it works over both Bluetooth and WiFi and ticks all the boxes we specified for the connection requirements for the watch.

As of iOS 7 and OS X Mavericks, AirDrop does not work between Mac and iOS. At WWDC 2014, Apple announced that this would be fixed with the release of iOS 8 and OS X Yosemite and that the platforms would be able to transfer data via AirDrop. 
How? Well the clue is they also announced that AirDrop would not work between Yosemite and Mavericks which indicates they rewrite the Mac side to match iOS. 
No surprise, then, that in this session, Apple announced the arrival of the Nearby Networking APIs to the Mac for Yosemite. AirDrop on Mac was probably re-engineered with these tools then and indeed I got some confirmation of this in the WWDC Labs.

In terms of our concerns here, the most interesting part of the Mac Nearby Networking API is that they support communication via Wifi and Ethernet but NOT Bluetooth. 
But how can this be? Surely the common interface between OS X and iOS is WiFI which requires you to be connected to a network? 
Well, as it turns out, no.

Ad-Hoc WiFi allows communication between devices without a supporting infrastructure, using peer-to-peer communication; it uses minimal power and supports multiple connections. 
I think this is the technology they're going to use.

A further piece of evidence is the list of iPhones that will connect to the watch. Note that are are also the devices that have Lightning connectors. Any iOS device that supports Lightning also supports Ad Hoc WiFi. Coincidence?
Consider the alternative: The missing device from the list of supported iPhones is the 4S, which can also run iOS8 and also supports Bluetooth LE but not Ad Hoc Wifi.
If they were using Bluetooth LE, why exclude the 4S?


The mobile devices* slated to pair with the watch all support iOS 8 and Ad Hoc Wifi.
New 'Nearby Discovery' APIs for the Mac don't support Bluetooth.
The watch is said to be able to connect to 'computers running iTunes'.

QED: Ad Hoc Wifi is the technology used to connect the watch to your iPhone and Mac.

*I don't know why they didn't mention the iPad, clarity maybe?

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