There is no doubt that even the most little of touches may set off this reaction. As an example, the father-in-law's garage has an empty plastic bottle that is hung from a length of thread; when the bottle comes into contact with the windshield, it is time to pull over ;). When my wife came to visit us last month, it was sufficient to trigger the same warning on the Mercedes-Benz Me app for our vehicle (I wonder whether it also makes use of the camera in addition to parking sensors, radar, and so on).