Android phones are not being sold yet, which makes the only phones with open, easily accessible third party development Windows Mobile phones (I dont believe the browser on Symbian phones are extensible in the same way). Google has taken advantage of this by releasing and expanding on their Gears platform for Windows Mobile, and has now released Search with My Location for Windows Mobile.
This software takes advantage of their cell tower database and Google Gears to make their Google search page location aware, meaning to do a localized search you only need to type the search term, as Google will already know more or less where you are.
The video below gives a (cheesy) idea of how the service works.
At the time of writing the service is only available in US and UK. Read more at GoogleMobile