In the (upcoming) 3G age, many applications such as multimedia streaming, file sharing and so on will be widely used in the wireless environments. In such a mobile environment, users may carry heterogeneous mobile devices with different transmission, ranges, latency, and even cache sizes. These devices not only can get services from a Mobile Support Station (MSS), but also they can form/generate a mobile peer-to-peer (P2P) network to provide services to each other. For such a mobile P2P network, an effective cache framework that can handle heterogeneous devices is required. In this paper, we propose a flexible cache scheme which is adaptive to the actual device condition and that of its neighbors. Our scheme encourages the "strong" peers to keep hot data and do service, and meanwhile to protect and best utilize the "weak" nodes with, their limited cache space. Simulation and mathematic analysis results show the effectiveness of our scheme.