There is an increasing tendency in sensor networks (and related networked embedded systems) to push more complexity and ‘intelligence’ into end-nodes. This in turn leads to a growing need to support isolation between the software modules in a node. In conventional systems, isolation is achieved using standard memory management hardware; but this is not a cost-effective or energy-efficient solution for small, cheap embedded nodes. We therefore propose a software-based solution that promises isolation in a significantly lighter-weight manner than existing software-based mechanisms. This is achieved by frontloading effort into offline compilation phases and leaving only a small amount of work to be done at load time and run time.