There have been many attempts at locating you indoors when GPS fails, but they usually come with catches. WiFi alone isn't very accurate, for example, while a ton of beacons isn't always practical. Mitsubishi may have a good answer to those problems, however: using two techniques at once. It just developed an approach that determines your location based on the time it takes for sound to reach positioning-capable WiFi access points. It's accurate to within 3.3 feet, and it works with as few as three hotspots -- which, of course, can get you online at the same time as they get you from A to B.