I have thought about this idea as well. It seems like the only feature left to add to an in-bay automatic (at this time). I have always wondered how it would do being installed under the dryer, if it would throw the prduct around the bay and some would get on your car.
Having no experience with a tire shiner at all, i have wondered how the wheels usually come out looking since the brushes always appear to be applying the product to the outer 2 or 3" of the wheels. Are they slimy when you exit, do they attract more dust and dirt if you dont get out an wipe them down after exiting?