intermittant wipers and auto dim mirror

would it be possible to add intermittant wipers, with adjustable delay speeds. basically all they are is a variable resistor, are they not? of course there would be some rewiring and adding new wires.
and an auto dimming mirror, im sure that is just a mirror with a 12v power source for the light sensor to dim the mirror. correct me if im wrong please.

my normal wipers are always either going to fast and screech or too slow and i cant see anything, and im just too lazy to flip the tap on the mirror.
i would really like to add a rear wiper, buts thats too much custom work.