NOVELTY - A fuel cell integrated on or into a unitary planar substrate comprises: (i) stacked layers comprising cathode layer and ion exchange layer on or within substrate; (ii) access path for allowing oxidant to access the cathode layer from a first side of the substrate; (iii) access path for allowing a fuel or a reaction medium containing a fuel to access a layer in the stack; (iv) conductor connecting to cathode; and (v) conductor connecting to access path for fuel.    USE - As a metal fuel cell or a hydrogen fuel cell integrated on or into a semiconductor substrate, an injection molded substrate or an integrated circuit substrate for an electrochemical power system (claimed).    ADVANTAGE - The invention integrates electrochemical power system on a substrate or fuel cell on a unitary substrate.    DETAILED DESCRIPTION - A fuel cell (502, 504) integrated on or into a unitary planar substrate having first and second sides comprises at least two stacked layers comprising:    (a) a cathode layer and an ion exchange layer situated on or within the substrate;    (b) a first access path for allowing an oxidant to access the cathode layer from the first side of the substrate;    (c) a second access path for allowing a fuel or a reaction medium containing a fuel to access a layer in the stack from the second side of the substrate;    (d) a first conductor (526) connecting to the cathode; and    (e) a second conductor (528) connecting to the second access path or the layer in the stack accessible through the second access path.    The ion exchange layer is oriented within the plane of the substrate.    INDEPENDENT CLAIMS are also included for:    (a) an electrochemical power system comprising fuel cell(s) integrated on or into the substrate and further including a third access path optionally different from the second access path for allowing egress of reaction product(s) from the layer; a regeneration unit (540) integrated on or into the substrate and comprising a reaction chamber (723) integrated on or into the substrate capable of holding reaction product(s) and having an interior and region(s) of ingress (532a, 532b) and region(s) of egress (534a, 534b), an anode (720) connecting to the interior of the reaction chamber, and a cathode (721) connecting to the interior of the reaction chamber; a first flow path interconnecting the third access paths of the fuel cells with the regions of ingress of the reaction chamber; and a second flow path interconnecting the regions of egress of the reaction chamber with second access paths of the fuel cells;    (b) a method of integrating a fuel cell on or into a substrate by placing at least2 stacked layers comprising a cathode layer and an ion exchange layer on a surface of a substrate; forming an access path to one of the layers extending inward from an opposing surface of the substrate; connecting a first conductor to the cathode layer; and connecting a second conductor to the access path or the layer made accessible by the access path; and    (c) a method of integrating a regeneration unit on or into a substrate by forming a cavity extending inward from a surface of the substrate and having an interior and regions of ingress and egress; connecting a first electrode to the interior of the cavity; and connecting a second electrode to the interior of the cavity.    DESCRIPTION OF DRAWING(S) - The figure shows a top view of an electrochemical power system integrated on or into a substrate.    Fuel cell (502, 504)    Substrate (506)    Anode cavity (518a, 518b)    First conductor (526)    Second conductor (528, 530)    Regions of ingress (532a, 53b)    Regions of egress (534a, 534b)    Regeneration unit (540)    Anode (720)    Cathode (721)    Reaction chamber (723)