We propose a cross-layer sensor network architecture to convert measurements acquired by a population of sampling devices, into synchronous sensor array measurements, using a network synchronization protocol that is inspired by the dynamics of pulse coupled oscillators (PCO). We study the specific application of these sensors in the distribution section of the Smart Grid as low cost Phasor Measurement Units, that we refer to as the Pulse Coupled PMUs (PC-PMUs). The paper studies the impact of synchronization error on the quality of the phasor measurements analytically and via numerical simulations, considering a solution in which sensing and synchronization signals are both over the power-line medium. The analysis is valid for generic networks where the connectivity is radial, and the numerical results are carried on a 33-bus test network representing a typical distribution feeder.