Requires ArcGIS 10.1.

To run the tool, open ArcGIS and navigate to the toolbox's containing folder (either using ArcCatalog or ArcMap's catalog window), double-click "FlowMapGenerator.pyt" to open the toolbox, then double-click "FlowMapGenerator" to run the tool.

More information available here: http://blogs.esri.com/esri/apl/2012/09/12/generating-distributive-flow-maps-with-arcgis/
