The growing trend of multi-device ownerships creates a need and an opportunity to use applications across multiple devices. However, in general, the current app development and usage still remain within the single-device paradigm, falling far short of user expectations. We present FLUID, a new multi-device platform that allows users to migrate or replicate individual user interfaces (UIs) of a single app on multiple devices. In addition, FLUID aims to require no extra development effort to support a wide range of legacy apps that follow the trend of using custom-made UIs. To this end, FLUID analyzes which UI states are necessary to correctly render UI objects, deploys only those states on different devices, and supports cross-device function calls transparently. In this demo, we demonstrate several interesting use cases supported by our Android-based FLUID prototype.