From Google:

Welcome to Google Voice Local Search

Google Voice Local Search is Google’s experimental service to make local-business search accessible over the phone.

To try this service, just dial 1-800-GOOG-411 (1-800-466-4411) from any phone.

Using this service, you can:

* search for a local business by name or category.
You can say “Giovanni’s Pizzeria” or just “pizza”.

* get connected to the business, free of charge.

* get the details by SMS if you’re using a mobile phone.
Just say “text message”.

And it’s free. Google doesn’t charge you a thing for the call or for connecting you to the business. Regular phone charges may apply, based on your telephone service provider.

Note: Google Voice Local Search is still in its experimental stage. It may not be available at all times and may not work for all users. We’re fine-tuning the service to get better at recognizing your requests. It’s currently only available in English, in the US, for US business listings.

If Google can iron out all the kinks in this technology, the possibilities will be endless. Why limit themselves to a mere phone directory. You’re already connecting to (and searching through) Google’s massive databases via a phone connection, why not pass them other search terms? For example, need to know John Adams birth date in a pinch? – Just bare with me.- With this technology, Google could simply forward the user’s query to a site like Wikipedia, or even use their own built in define operator, i.e., define: John Adams. Now all Google would have to do is read you the results, which is what they are already doing in Goog 411.

It will be interesting to see where they take this.