Note: It does look like you can utilize parameters to achieve this somewhat; i.e., create a parameter with these types of names/values
Area 1 / ?extraParameter1=someValue&extraParameter2=anotherValue
Then, put your parameter onto one of your panels and render it. Then, in your dashboard, goto the externally hosted url panel, tell it you want to edit your URL, and your parameter value will be available. You'll need to appropriately craft your values to http compliant values, but that isn't too difficult.
I still haven't figured out / if you can go *back* from an external host to a panel hosted in tableau server. . . . .
Brian, Tableau has the ability to connect to GIS data warehouses using two different methods: one is through adaptation of the TMS file; the other is through WMS.
A solution that may interest you is available here:
To understand this concept: The solution allows you to bring in background basemaps, layered groups, "middle layers" and then use Tableau to analyse foreground "layers" which are basically ESRI SHP files that have been converted to Tableau ready format (Polygon, Line, Circle, Shape) etc.
The scope of this solution is really limited to a local installation though - scaling this to the enterprise level isn't really practical, because really, it's about serving up the tiles.
You are also correct about URL parameters. It's possible to display Google Maps and other 3rd party maps using this method, but analysing your data using this method is limited. I suspect you want to analyse your shapes and points.