My hearing is crap. I know this, it stinks, whatever, I deal with it.
Sometimes, though, it's a pain - like when my kids are in the backseat of the minivan and I can't hear them over the road noise.
I know that noise cancellation technology isn't particularly complicated - you need a mic, a processor to create the cancelling signal, and a speaker. ANC headphones work great. And I know that some cars build ANC into the stereo. But since I don't have that.... this would be awesome: An ANC system that I could plug in to the car's aux port. Plug it in, turn the stereo to aux, and constant-frequency noises (like wind and road noise) are greatly reduced. Obviously, I couldn't listen to the stereo while it was on, but we don't listen to music that much in the car.
Does this exist? It seems like it would be useful. Google wasn't much help.