As the possession of personal mobile devices has recently become commonplace, the mobile device can act as a mediator between users and services in users' environment and the opportunities, and possibilities for collaboration with mobile devices could also be augmented. We present the project Celadon, an infrastructure to enable on demand collaboration between heterogeneous mobile devices and environmental devices. In this paper, we describe the vision and architecture for Celadon in detail and core components we have implemented to date.