You mean an indicator that can easily be analyzed... right in front of your eyes... maybe like wipers on the windshield that are not moving on a consistent interval?
I have to agree with PACECAR on this one. The light on the wiper stick is not easily visible. I have left it ON when leaving the car, especially if its just a drizzle and the wiper doesn't come on that often. I forget to turn it OFF cuz I don't realise its turned ON. Once my neighbour knocked on the door to tell me my wiper was still ON