In recent years, there has been a growing interest in designing mobile systems consisting of special relay nodes whose mobility can be controlled by the underlying network. In this paper, we consider the design of a heterogeneous mobile ad hoc network (MANET) consisting of two kinds of mobile nodes - the traditional nodes with limited energy and a few mobility controllable relay nodes with relatively abundant energy resources. We propose the relay deployment problem that aims to optimally position these relay nodes in the network so as to minimize the overall power consumption for data transmission at the traditional nodes. We present a mobility prediction based framework to solve to the relay deployment problem in a truly mobile network. We investigate the performance of the proposed framework through extensive simulation study using three different mobility prediction schemes. We also perform experiments to understand the tradeoffs involved in deploying an increasing fraction of such relay nodes in the network. Results indicate that even when the relay nodes constitute a small percentage of the total nodes in the network, the proposed framework results in significant energy savings.