The new IDX Google Polygon Map Widget allows you to create a map widget that can be filtered using the polygon tool. We've added it to this site, take a look: https://pmlsales.com/newest_listings.html
You can get access to this widget, along with all of the apps we offer at idxaddons.com, for free, if you make us your IDX Broker developer. All you need to do is send developers@idxbroker an email that says "We want to use RealtyCandy as the IDX developer on our IDX accounts." It's fast, free and easy.