Abstract: Systems for interconnecting two or more electrochemical devices such as fuel-to-energy conversion devices are described. A unitary manifold structure can include a manifold for delivery of a reactant gas to two or more devices, and/or electrical circuitry addressing the two or more devices. Electrical circuitry can be provided in combination with conduits for delivery of reactant gases. Inter-device connecting apparatus can define boundaries for separation of at least two reactant gases addressing the devices, and a plurality of inter-device connecting apparatuses can be interconnected themselves to form larger arrangements of essentially infinite size.