Adjustable seat weight sensors

In light of all the children that have parished in hot/cold cars, I pose to you this idea.  All passenger seats can be equiped with an adjustable weight sensor.  Each seat has its own sensor that can be zeroed out like a scale (via the info center or the radio controls as in the Mustang for example).  The need for it to be zeroed out like a scale is to be able to accomodate any carseat (they don't all weigh the same).  The driver puts the carseat in and properly straps it in place.  The driver then accesses the info center/radio controls, selects the correct seat and sets it to zero.  When the driver has a passenger in that seat, turns the ignition off, gets out of the vehicle and closes the door; the sensor sends a signal that the weight did not go back to zero, implying that there is still a passenger in the vehicle.  There is a 30 second delay before the car alarm goes off with lights flashing to remind them that they have forgotten a passenger (a chime may not be loud enough for those of us that are hearing impaired and the lights are visible day or night).   As the child grows and the carseat is changed, the system can still be used because it can be rezeroed every time and also used without a child carseat or booster seat. Adding an "off" setting for people that don't have children and/or for seats that will have adults in them should also be an option for each individual seat.