https://techcrunch.com/2017/09/12/the-new-apple-watch-series-3-has-cellular-built-in/

The new Apple Watch is now official, offering one big highlight upgrade over the previous version: Built-in cellular support. Wireless cellular LTE connectivity provided by a built-in chip means the new Apple Watch will be able to stay connected even when it’s not tethered to an iPhone, which is a huge step forward in terms of making it an independent mobile device.

Pricing for the Series 3 Cellular starts at $399, and a version without cellular starts at $329. Pre-orders begin on September 15, and they’ll be available on September 22. The cellular version can be used without an iPhone at all.