Well, there are lots of pollutants in indoor air. Obviously it's possible to buy a carbon monoxide monitor for every home right now to provide warnings in case of danger. That's one example of a successful area.
I don't think you'd ever get to the point where you could monitor every home continuously. The radon issue is one that needs to be addressed and radon can be tested in homes. You don't need it done on an ongoing basis, but you just need to know how high the levels are and then act appropriately.