One patent on file
Other more detailed patentable ideas might be pertinent. Perhaps a simple modulated laser diode shining near the critical angle of refraction for the windshield at that light frequency. When moisture collects on the windshield the dispersion pattern will change and the laser light will be detected by a shielded and filtered phototransistor. Because the light is modulated, this makes the effects of the Sun of little consequence.

This exists on higher end cars.

However, I love how your phrased it. I'm sure the BMW manual doesn't have quite the same delivery. Keep up the good work.

It is needed but there is the cost component. But there is a flip side... the more idiots features you add on to the car itself the higher the price tag till finally you price all the "idiots" out of driving at all.

Well, the more idiots off the road, the better, I say. This idea seems to permit more of them, though, but not to the point where it "replaces" better sense.

No sensor is needed. If headlights are a problem Daytime Running Lights (which illiminate when the engine is running) will do.

Otherwise, the electronics to do so would be simple and cheap enough in quantity. ro not be a concern.

Just leave the headlights on all the time. This is a legal requirement in some countries; and in those places the headlights are often wired to come on when the ignition is turned on - easy.

Its a good idea all the automaker would have to do is make the lights come on when you turn the wipers on for more then 20 seconds. It's that simple