Good idea, how often do you check your tire pressure? Not a day goes by while driving do I not see tires that are under inflated, so having that gage in the compartment does little good unless used. With runflat tires the side walls are stiff enough that you can't visually "gage" the tire pressure. Since I like a car to run at peak tune, that includes tire pressure, it is a simple matter to check them while running down the road. I check my tire pressure nearly every time I drive the car. It took very little time to read the correct way to recalibrate the sensors and it takes less time that checking the pressure with a gage. On a trip through the Rockies I hit a sharp stone very hard and was able to bring up the tire pressure and watch it until I was where I could get safely off the road and out of traffic to check for damage. At that point the cost of the pressure sensors was cheap to say the least.
Another system I see coming on line looks even better. It senses the rotating radius of all of the tires, ties into the braking and traction control system, and if it varies enough it will bring up a "low tire pressure" message on your DIC. By utilizing the systems already in place and working with the programming it brings about a very good and inexpensive warning system.
I miss my Cadillacs - ;-(