I have a iPod touch WiFi and would like to use Google Maps with GPS for driving.
Question: is there an external bluetooth GPS antenna that will allow for this?
I would be surprised if there was a product that would integrate with Google Maps like the one your described. Google Maps is designed to work with Location Services, and because of the sandboxing, and limitations that Apple has implemented for your security, I doubt that an external unit could function as Location Services.
That said, it would make sense if there were 3rd party applications designed to work with external units.
Take a look at this http://xgps150.dualav.com/
My friend has this and he is using it with an app named Navigon (http://www.navigon.com/portal/int/produkte/navigationssoftware/mobile_navigator_iphone_eu.html)
I am not sure whether it works with inbuilt google maps, He is using Navigon for voice navigation and other useful features of Navigon.
Hope this helps and answers your question