Smartwatches give people lightweight and immediate access to messages, notifications, and other digital data while on the go. While already powerful as standalone devices, the capabilities of smartwatches increase significantly when used in tandem with other devices that people carry, such as their phones or tablets, which allows for novel cross-device interaction techniques. However, so far there are only a relatively small number of explorations into watch-centric, cross-device interaction techniques. Building and exploring cross-device interaction techniques and applications is a difficult task, as most existing development kits have only limited support for input gesture recognition, different sensor hardware configurations, rapid interface designs, or cross-device connectivity and transfer of information.

To bridge the gap between concept design and full im-plementation, we introduce WatchConnect, a rapid prototyping toolkit for watch-centric cross-device interaction techniques and applications (Figure 1). The toolkit provides (i) a modular and extendable hardware plat-form that emulates a smartwatch, (ii) a runtime system and user interface components that support quick prototyping of watch interfaces using an existing UI frame-work, and (iii) a rich set of input and output events and gestures using a range of built-in sensor mappings and simulators. The contribution of this paper is a novel approach for rapidly prototyping and designing smart-watch-centric cross-device applications and interaction techniques, using simulated hardware and software building blocks.