Apple has a secret app in the App Store which allows some iPhone users to map the interior of a building using their handset. First discovered yesterday by developer Steve Troughton-Smith, an app called Indoor Survey has been available on the App Store since last week.
The software is currently hidden in the App Store and is not operational, suggesting that the official launch is around the corner.
Basically a funnel for Apple's MapsConnect website, the app appears to act as a crowdsourced Ground Truth service aimed at improving the accuracy of Apple Maps data when it comes to indoor maps.