With the rapid evolution of mobile and ubiquitous computing, small-scale devices like personal digital assistants, smart "converged" phones and laptops now dominate the market. Despite the parallel emergence of the grid as the new distributed computing infrastructure, an integrated hybrid grid system that consists of both traditional fixed nodes but mobile and limited devices as well, has only recently gained some popularity. One of the main challenges in realizing this integration is the very low levels of reliability and availability of small scale and mobile devices -a characteristic that could compromise the overall dependability and performance of the whole grid system. In this paper we try to identify the main dependability requirements for such a hybrid grid system. We then present our own approach to an efficient integration using our virtual clusters platform, and explain how we manage to meet the dependability requirements as set by our research.