well i'm really no good at this sorta thing, but would it not be possible to set up a simple and dirty script, forget trying to tie it in to when alsamixer resets the volume, get it to run every 30seconds, you cant max it any more than max so whats the harm if its ran more often than necessary? obviously not running all the time, but a qbw you press to start and stop the recurring widget when you get in and out of the car.