Hmmm. Can see the problem easily enough NeilN. One would tire...

Hmmm. Can see the problem easily enough NeilN. One would tire quickly of climbing the ladder with bucket & mop whatever.
This sort of problem is not un-common but having a windscreen wiper with water jets & all sounds a bit fruity.
The nearest thing that comes to mind was a 'supposed' claim by Mercedes Benz some 20 tears back or so, that the shapeing of the lens on their tail & brakelights was "self cleaning"!

The idea relied on some combination of wind & rain with the water getting sluiced along these horizontal grooves.
I recall Ford copied the general thing a year or two later.
Did it ever really work though?
Maybe there's enough regular rain in Germany to get some result and driving at outrageous speeds along the autobahns providing the wind component.

geojac