The ability of electrochemical sensors to properly measure wall shear stress is here considered for using these sensors as potential candidates for time-resolved estimation of the large-scale activity occurring in the flow separation region downstream of a bump. The inflow Reynolds number considered, based on the channel full height and the incoming bulk velocity, is 1735. The methodology implemented consists in combining the electrochemical sensors with particle image velocimetry (PIV) measurements and to build a model estimate of a low-order representation of the flow field. The model estimate is based on a multitime reformulation of the complementary technique. The present paper shows the potential of electrochemical sensors for properly resolving the low-frequency flapping mode whose control was recently shown to be a potential candidate to significantly reduce separation.