watchOS 2, which further allows third-party native apps to run smoother and faster, arrives as a free software update on September 16. September 16th is also the date when the Watch would be made available for sale in 24 countries. A portion of the sales from the Watch goes to the Global Fund against AIDS. 
While Smart Replies or emoji, and Digital Touch are some of its other features, the Apple Watch requires iPhone 5, iPhone 5c, iPhone 5s, iPhone 6 or iPhone 6 Plus, iPhone 6s and iPhone 6s Plus with iOS 8.2 or later to run.