A large class of delay tolerant sensor-net applications require reliable deliver of every data point. The nature of sensor network deployments makes providing reliability a challenge. Harsh environments and unreliable wireless communication can cause long periods of poor to no connectivity. Meanwhile, energy and resource constraints on sensor platforms limit retransmissions and buffer sizes. This paper presents an architecture designed for these challenged networks. The architecture provides packet-level, hop-by-hop reliability for delay-tolerant data using sequential storage for buffering during long queue delays. The concepts discussed in this paper are implemented as services in the Extensible Sensing System, a deployment at the James Reserve as part of the Cold Air Flow Project.