Dave Plowman (News) submitted this idea :
My last two cars have had them - rain sensing. But they cancel when you
switch off the engine - even if you leave the switch in that position. You
have to reset the switch after starting the engine. Anything else would be
stupid.

FWIW, neither system worked as well as I'd like. Despite several settings,
often wouldn't trigger with a wet screen.

My car has them, they work perfectly and are inhibited if you restart
the engine. The switch has to be reset to put them back on to auto.