https://arstechnica.com/gadgets/2017/09/apple-watch-series-3-review-skip-the-lte-headaches-for-now/

Ahead of Apple's September event, some things about the high-end iPhone X remained a mystery despite a lot of pre-event rumors regarding the $1,000-plus smartphone. On the other hand, the Apple Watch Series 3 proved entirely predictable—we knew its distinctive feature would be standalone LTE service.WatchOS 4WatchOS 4 is the latest software update to hit all Apple Watch models. The Series 3's launch coincided with its rollout. However, only a few things are unique to the Series 3 Watch models on watchOS 4: LTE service, Siri speaking, and barometric altimeter calculations. We'll be discussing all aspects of the Apple Watch Series 3 in this review, but read our watchOS 4 review for full details on the latest software update.

Wearables with LTE connectivity aren't new, but the feature is new to the Apple Watch. So the move still marks a huge update to an Apple device that's been around for less than three years. And it's a big gamble for Apple considering other wearable manufacturers have tried (and largely failed) to make a good cellular wearable experience.