A instance of a runtime environment at each of a first and second computing device can allow an application at the first computing device to access hardware resources of the second computing device via the runtime environment. For instance, one device can comprise a mobile device and the other device can comprise a desktop computer, a laptop computer, or a home entertainment device. The first and second instance of the runtime environment can be configured to communicate with one another through a common messaging format of the runtime environment. For example, an editing or design application at one device may use a touch-enabled display at the second device to select tools, manipulate 3-D representations, or otherwise provide input data. As another example, a game at a mobile device can use the runtime environment to provide visual and audio output using a television set-top box running the runtime environment.