Further, in most cases, the UICompanion app performed comparably or better than the corresponding companion app both in terms of qualitative metrics, including latency and energy, and quantitative metrics, including look-and-feel. The lines-of-code required for the developer to specify the UI design in UIWear is an order-of-magnitude smaller compared to the companion app lines-of-code. We evaluate 20 developer-written companion apps from the AndroidWear category on Google Play against the UIWear-created UICompanion apps. We implemented UIWear on Android smartphones, AndroidWear smartwatches, and Sony SmartEyeGlasses. Our UIWear system abstracts a logical model of the smartphone GUI, re-tailors the GUI for the wearable device based on the specified UI design, and compiles it into a companion app that we call the UICompanion app. The developer writes an application for the smartphone, but only specifies a UI design for the wearable. This paper argues for a different programming model for wearable devices. The development effort required to write a companion app is significant and will not scale to an increasing diversity of form factors. However, the current wearable programming model requires the developer to write a custom companion app for each wearable form factor the companion app extends the smartphone display onto the wearable, relays user interactions from the wearable to the phone, and updates the wearable display as needed. Wearable devices such as smartwatches offer exciting new opportunities for users to interact with their applications. We have built a Cider prototype, and demonstrate that it imposes modest performance overhead and runs unmodified iOS and Android applications together on a Google Nexus tablet running the latest version of Android. Diplomatic functions leverage per-thread personas, and allow foreign applications to use domestic libraries to access proprietary software and hardware interfaces. Compile-time code adaptation enables existing unmodified foreign source code to be reused in the domestic kernel, reducing implementation effort required to support multiple binary interfaces for executing domestic and foreign applications.

This is accomplished using a novel combination of binary compatibility techniques including two new mechanisms: compile-time code adaptation, and diplomatic functions. Cider enhances the domestic operating system, Android, of a device with kernel-managed, per-thread personas to mimic the application binary interface of a foreign operating system, iOS, enabling it to run unmodified foreign binaries. We present Cider, an operating system compatibility architecture that can run applications built for different mobile ecosystems, iOS or Android, together on the same smartphone or tablet.

Cider for android