Wow! That cut out is so small and so close to the windshield, it probably would be almost impossible to see on a dark color dash cover with the black dash underneath. I have no idea what the sensor is for, but we obviously don't have it on North American Fits (unless one of the Canadian models has the sensor).

 

I just got my cover from coverking and I'm a little disappointed that the cover doesn't extend as far down on the passenger's side as I thought. I can scour the forums later to try and link the pic but I think it was another FitFreak that had a Fit logo embroidered on their cover where it actually extended as low as the "pen-holding" ridge. Mine only goes about as far down in front of the passenger as top vents.