1. A method for implementing a user interface (UI) at a client device, comprising: receiving encoded UI video assets via a predefined video transport channel; at a UI renderer, decoding said received UI video assets to produce a video presentation stream suitable for use by a display device; at a message proxy, in response to receiving user interaction data indicative of a local function, invoking an application programming interface (API) associated with said local function to select an appropriate channel of said video presentation stream.