This paper proposes a mobile pipeline computing concept in a Device-to-Device (D2D) communication setup and studies related issues, where D2D is likely based on millimeter wave (mmWave) in the 5G mobile communication. The proposed opportunistic system employs a cluster of pipelined resource-limited devices on the move to handle real-time on-site computation-intensive tasks for which current cloud computing technology may not be suitable. The feasibility of such a system can be anticipated as high-speed and low-latency wireless technologies get mature. We present a system model by defining the architecture, basic functions, processes at both system level and pipeline device level. A pipeline path finding algorithm along with a multi-task optimization framework is developed. To minimize the search space since the algorithm may need to be run on resource-limited mobile devices, an adjacencymatrix-power-based graph trimming technique is proposed and validated using simulation. Preliminary feasibility assessment of our proposed techniques is performed using experiment and computer simulation. As part of feasibility assessment, the impact of mmWave blockage on the pipeline stability is analyzed and examined for both single-pipeline and concurrent-multiplepipeline scenarios. Our design and analysis results provide certain insight to guide system design and lay a foundation for further work in this line.