Apple Watch is a line of smartwatches designed, developed, marketed and sold by Apple Inc. It incorporates fitness tracking and health-oriented capabilities with integration with iOS and other Apple products and services. Apple Watch uses a wireless connection to an iPhone to perform functions such as calling and texting, and can independently connect to a Wi-Fi network for some tasks. Series 3 and later LTE Apple Watches can independently connect to a mobile network, largely obviating the need for an iPhone after initial setup. Apple Watches are not entirely dependent on what series they are for iPhone compatibility, rather, they are dependent on the version of watchOS that they are running. All currently manufactured Apple Watches come with watchOS 6 preinstalled, and as such require an iPhone 6s or later with iOS 13 or later. The Apple Watch was released on April 24, 2015 and quickly became the best-selling wearable device: 4.2 million were sold in the second quarter of fiscal 2015. The second generation of Apple Watches was released in two tiers in September 2016 — the Apple Watch Series 1 and Apple Watch Series 2 — while the first generation was discontinued. The Apple Watch Series 3 was released on September 22, 2017, when the Apple Watch Series 2 was discontinued. The Apple Watch Series 4 was announced on September 12, 2018; Apple Watch Series 1 was discontinued. The Apple Watch Series 5, announced on September 10, 2019, became available on September 20, 2019. Series 4 was discontinued. Apple Watch Series 3 now sells at a lower price-point.