You can export several kind of map from mesh within Unity using the Texture Exporter. Select the Polaris/Texture Exporter menu, you will see a window appears as below:
Fill in appropriate parameters, then hit Save, you will see the map appear in the selected directory.
This tool can export map from a Mesh or a Mesh Filter.
Currently support texture types: Uv Layout, Vertex color.
More texture type will be added in future updates.