Path Guide: A New Approach to Indoor Navigation
microsoft.com
microsoft.com
The original researchers have started a PaaS solution providing an API that you can hook into your apps today, allowing you to get (lat, lng) coordinates inside mapped structures. One needs to build path-finding on top of that though.
This would also work well for an airport.
The most interesting feature to me is the ability to add annotations along the way. I'd use that to describe wayfinding points, such as "the elevator" or "the giant ice cream cone."