The number of networked smart devices available in everyday environments is rapidly increasing; however, many current devices adopt mutually incompatible networks, protocols, and application programming interfaces. As such, creating mobile applications that dynamically discover and integrate ambient functionality across multiple vertical markets remains challenging. In this paper, we introduce a novel middleware framework, called Ambient Control, which enables commodity mobile devices (e.g., smart-phones) to dynamically mediate control messaging between incompatible smart devices situated in the user's environment. Ambient Control enables a variety of control capabilities and protocol translation services to be dynamically installed into a user's mobile device on-demand using plug-ins. The approach also features an intuitive "Tap to Interact" workflow that allows a user to tap nearby smart devices with a smart-phone to install required interaction plug-ins and automatically "wire" them together in interesting and potentially unforeseen ways. In this paper, we present a detailed overview of the Ambient Control framework, introduce our fully functional prototype, and present an evaluation indicating that the prototype provides efficient messaging performance and imposes low processing and memory overhead, making it suitable for deployment on many commodity mobile devices.