I have a 2009 base cooper hatch and there is what looks like a sensor of sorts on the rear view mirror. It's the same one as circled in the picture below. I do not have a rain sensor so this must be something else. The reason I am interested is because my parking pass is there covering it most of the time and I have not noticed anything, but would like to find out if it's actually used for something.

 

That might be the sensor for the auto dimming, I will have to look on my 07 and see if it is there. One thing I am learning about Mini's is that just because something is there doesn't mean it is really there. Lots of buttons on mine that do nothing ie bluetooth, etc

 

Front light sensor, you have a manually adjustable rear view mirror, so it does not use it.

 

Thanks! I had a feeling that's what it was but was not sure. I do not have auto dimming mirrors so it's fine to have that sensor covered up by the parking pass.