The simplest method is to include the KML file. But, this KML approach in Google Maps API is not support Dynamic KML, it will have no effect. The JAK Java API for KML can generate KML file.
Second method is using JSON data from geocodezip.com. This can work very well at dynamic polygon.
Last method is using XML data from XML Parsing at Google Demo Gallery. This can also work very well at dynamic polygon.


