Bimetallic nanoparticles (BM-NPs) have attracted much attention in catalysis, sensing, and electronics as a result of their ultra-high activity for surface reactions. For reliable utilization of BM-NPs in various applications, robust synthetic methods for the creation of non-aggregated functional BM-NPs with diameters less than a few nanometers are needed. Herein, we present functional assemblies of ultra-small BMNPs produced within high-stability porous ion-exchange polymers. Specifically, PdPt NPs can be readily produced with precision dimensional control down to 1 nm. These PdPt NPs with porous polymers display superior hydrogen (H-2)-sensing properties at room temperature in air We achieve an ultra-low limit of detection (H-2 0.4 ppm), thereby confirming the outstanding sensing performance of the PdPt NPs. We further demonstrate a wireless H-2 -sensing system by combining porous polymer-templated PdPt NPs with a radio-frequency identification (RFID) system, which enables the wireless detection of H-2 in a sealed gas head space.