The Apple W2 moved the W series onto the wrist, built directly into the Apple S3 System in Package rather than shipped as a discrete chip. Apple credited it with 85 percent faster Wi-Fi and half the Bluetooth power draw — headroom the Series 3 spent on its defining feature, the first LTE Apple Watch.
The W2 set the integration pattern: from here the Watch's wireless silicon lived inside the SiP, invisible in teardowns and inseparable from the S chip it served. One generation later the Apple W3 made the arrangement standard.
