We claim that Delay-Tolerant Networking has the potential to form an internetworking overlay that shapes traffic in a manner that exploits the capacity of last hop wireless channels and allows for energy-efficient internetworking. We demonstrate DTN potential for energy-efficient internetworking through an overlay-architecture and a tool we have developed that captures the required state transitions of the mobile device WNIC. We show experimentally that the DTN overlay can re-shape traffic in a manner that allows the receiver to exploit the energy-throughput tradeoff better: it may condense sporadic packets into a burst and, in return, prolong sleep and power-off duration without risk to miss incoming packets and without degradation in throughput.