Steve Jobs told that the Maps application on the iPhone (and iPod Touch) works with Google Maps. The third element in the solution is SkyHook Wireless. They have a databse of WiFi Access points and their location. So when the iPhone's WiFi is turned on and it receives signals from an access point, it will be able to find out where you are.
Skyhook has a piece of laptop software of it's own that works as a browser plug-in.
It'll show me where I am, based on the same access point database.
The mash-up below is a logical next step: