We explore, to the best of our knowledge, the potential of diffractionless subwavelength grating waveguides for sensing applications. We show that by subwavelength patterning of silicon-wire waveguides the field delocalization can be engineered to increase the sensitivity. Fully vectorial 3D-FDTD simulations confirm the sensitivity enhancement, achieving sensitivities of 0.83 RIU/RIU and 1.5·10(-3) RIU/nm for bulk and surface sensing, respectively, which compare favorably to state-of-the-art sensing waveguides.