According to Technology Review:
Broadcom has just rolled out a chip for smart phones that promises to indicate location ultra-precisely, possibly within a few centimeters, vertically and horizontally, indoors and out.
The unprecedented accuracy of the Broadcom 4752 chip results from the sheer breadth of sensors from which it can process information. It can receive signals from global navigation satellites, cell-phone towers, and Wi-Fi hot spots, and also input from gyroscopes, accelerometers, step counters, and altimeters.
The variety of location data available to mobile-device makers means that in our increasingly radio-frequency-dense world, location services will continue to become more refined.
In theory, the new chip can even determine what floor of a building you're on, thanks to its ability to integrate information from the atmospheric pressure sensor on many models of Android phones. The company calls abilities like this "ubiquitous navigation," and the idea is that it will enable a new kind of e-commerce predicated on the fact that shopkeepers will know the moment you walk by their front door, or when you are looking at a particular product, and can offer you coupons at that instant.