Mappedin can continue to function when the user goes offline after the map is loaded. The entire map is downloaded, so switching between buildings while offline is supported.
All directions are calculated locally on the device, no Internet connection is required for that.
The main thing that would be affected would be any images that are loaded on demand (i.e. images added to a Location) as well as the outdoor map. Outdoor tiles are also downloaded on demand, so for example if the user zooms in or out the outdoor map may not update to show more or less detail.