Exploiting mobility improves the energy efficiency of data collection in wireless sensor networks (WSNs) for many applications. As more and more multimedia sensor nodes, equipped with audio and video capture capabilities are employed to characterize a sensing environment, streaming data are becoming increasingly important in WSNs. However, the mobility of MEs poses challenges on how to efficiently provide uninterrupted message delivery for continuous data streams in WSNs. In this paper, we propose a seamless streaming data delivery (SSDD) protocol for multihop cluster-based WSNs with MEs. Different from existing works, we concentrate on the localized mobility support for the delivery of streaming data in hierarchical WSNs. By introducing a cross-cluster handover mechanism and a path redirection scheme, SSDD efficiently maintains the end-to-end connectivity between a source and a ME during data transmission while avoiding most of the overhead in broadcasting the location of the ME as it moves in the sensing field. Extensive evaluation results demonstrate the effectiveness and high scalability of SSDD in terms of both energy efficiency and delivery latency.