The Apple Watch Series 3 includes cellular connectivity, but SMS messages are not treated the same way as phone calls and iMessages. Here's what you need to know.
If your texts are green (SMS) and they're not sending, there's a reason why.
The big new feature on the Apple Watch Series 3 is its ability to live on a cellular LTE network, free from both Wi-Fi networks and the need to be paired to an iPhone. I've been living with the Watch for about two weeks (read my Apple Watch Series 3 review here), and I haven't experienced the sort of wireless problems that some other reviewers have.
But I have experienced some quirks, particularly with text messages, and investigating them revealed some limitations in how the Apple Watch handles its wireless interactions.
If you didn't know the various Apple Watch connection cans and can'ts, you might drive yourself crazy wondering why one thing works and another thing doesn't. Apple outlines how the Series 3 with LTE works on a support page that goes through a pretty specific rundown. (CNET's Brian Tong and I cross-tested on various watches and phones.)
TL;DR: The Apple Watch really, really wants your phone to be powered on somewhere, connected to Wi-Fi or LTE. That location doesn't have to be anywhere near the Watch, however. Your iPhone can be sitting on your nightstand at home, and you could be 50 miles away -- though, obviously, someplace that still has cellular coverage.
Here's how your texting experience will differ, depending on the status of your iPhone.
Blue messages (iMessage) work all the time over LTE.
Same as above. EXCEPT:
Everything should feel similar to how the Apple Watch already worked before over Wi-Fi when your phone isn't directly paired via Bluetooth. Much like Google's Android Wear watches, the Apple Watch works remotely.
Business as usual.
iPhone X: Everything you need to know.
Apple Watch Series 3 review: A dash of iPod and a bit of iPhone for your wrist.