Edge networks such as sensor, mobile, and disruption tolerant networks suffer from topological uncertainty and disconnections due to myriad of factors including limited battery capacity on client devices and mobility. Hence, providing reliable, always-on consistency for network applications in such mobile and sensor systems is non-trivial and challenging. However, the problem is of paramount importance given the proliferation of mobile phones, PDAs, laptops, and music players. This thesis identifies two fundamental deterrents to addressing the above problem. First, limited energy on client mobile and sensor devices makes high levels of consistency and availability impossible. Second, unreliable support from the network infrastructure, such as coverage holes in WiFi degrades network performance. We address these two issues in this dissertation through client and infrastructure end modifications. The first part of this thesis proposes a novel energy management architecture called Hierarchical Power Management (HPM). HPM combines platforms with diverse energy needs and capabilities into a single integrated system to provide high levels of consistency and availability at minimal energy consumption. We present two systems Triage and Turducken which are instantiations of HPM for sensor net microservers and laptops respectively. The second part of the thesis proposes and analyzes the use of additional infrastructure in the form of relays, mesh nodes, and base stations to enhance sparse and dense mobile networks. We present the design, implementation, and deployment of Throwboxes a relay system to enhance sparse mobile networks and an associated system for enhancing WiFi based mobile networks.