A wide variety of applications are envisioned and demonstrated with artificial micro‐ and nanomachines, ranging from targeted drug or gene delivery, microsurgery, environmental sensing, and many more. Here, it is demonstrated how helical nanomachines can be used to measure and map the local mechanical properties of a complex heterogeneous environment. The positions of the nanomachines are precisely controlled using externally applied magnetic fields, while their instantaneous orientations provide estimation of the viscosity of the surrounding medium with high spatial and temporal accuracy. The measurement technique can be applied to both Newtonian as well as shear thinning media, and all experimental results are in good agreement with the theoretical analysis. It is believed that this novel application of helical nanomachines can be particularly relevant to biophysical studies and microfluidic technologies.