Your shiny new Apple Watch Series 3 may make and take phone calls via its own inbuilt 4G cellular smarts, but don't get too used to leaving your iPhone behind when you head overseas.
The unique nature of the Apple Watch LTE model means that it runs independent of your iPhone only within Australia (and, as we understand it, not even on all the mobile phone bands used around the country – something worth checking with your carrier of choice before plonking down your cash).
Once you set foot abroad and rely on global roaming to stay connected, the Apple Watch loses its stand-alone smarts and must rely on a Bluetooth link to your iPhone.
The story behind this: the Apple Watch doesn't use a conventional SIM card with its own number. Instead, it's built around 'eSIM' technology which you can think of as a virtual SIM card which your carrier links to your actual mobile phone number, so the watch and iPhone share the same number
(That link costs extra, by the way: Telstra's 'One Number' system and Optus' similar 'Number Share' each adds a $5/month surcharge to your current plan; Vodafone will launch its own Apple Watch eSIM plans in December but has yet to share the add-on pricing.)
The lack of international roaming might not be a deal-breaker: you'll still be able to piggyback onto your iPhone, just as a standard non-LTE Apple Watch can do.
It's just that the lack of international roaming will cruel the appeal of temporarily leaving your iPhone behind while you hit the gym or go for a run, and relying on the Apple Watch's 4G capabilities to stream music, take phone calls or deal with text messages.