Currently, access to Grid services is limited to resourceful devices such as desktop PCs but most mobile devices (with wireless network connections) cannot access the Grid network directly because of their resource limitations. Yet, extending the potential of the Grid to a wider audience promises increase in flexible usage and productivity. In this paper we present a middleware architecture1 that addresses the issues of job delegation to a Grid service, support for offline processing, secure communication, interaction with heterogeneous mobile devices and presentation of results formatted in accordance with the device specification. This is achieved by outsourcing the resource intensive tasks from the mobile device to the middleware. We also demonstrate through formal modeling using Petri nets that the addition of such a middleware causes minimum overhead and the benefits obtained outweigh this overhead.