they have really cracked down on the wiper light thingys around here, they have all but dissapeared.
Like you said its up to the cop to decide if its worth a traffic stop or not, my guess is 90% of the time its not.
Come on how many items have you bought for your truck that is "for off road use only" hell every light on my truck said that on the package, many engine bolt on's say the same thing. Easy to sell them....