Next-generation Grid applications will operate within and across many heterogeneous network types; will employ a wide range of device types ranging from supercomputers to sensor motes; and will require many more “interaction paradigms” than merely RPC and messagepassing (e.g., publish-subscribe, multicast, tuple spaces etc.). In this paper, we propose a middleware approach to meeting these emerging needs. Our approach is to provide a highly flexible “overlay network framework” that underpins an extensible set of plug-in interaction paradigms. The middleware is structured using a lightweight run-time component model that enables appropriate profiles to be configured on a wide rage of device types, and facilitates runtime reconfiguration (as required for reasons of adaptation to dynamic environments). For proof of concept, we are exploring a wildfire scenario which involves mobile groups of firefighters, mobile sensors, control centres, and access to parts of the wider fixed Grid for simulation. We are also investigating the application of our approach more generally in the management of the “e-Environment”.