Picture this: You’re out running errands when you remember you’re fresh out of stamps. Time to drop by the nearest post office, which is … where, again?

Sure, you’ve got your iPhone handy, but you’d rather not deal with tapping out a search query while you’re standing in front of the grocery store. But what if you could fire up an iPhone app, tap a button, open your mouth and ask?

That’s the idea behind Dragon Go, a new—and free—iPhone application from the speech recognition gurus at Nuance.

Available now in the App Store, Pandora Go! couldn’t be easier to use: just tap the red “record” button, ask your question, and the app quickly serves up a bevvy of answers from sources ranging from Amazon and Google to Wikipedia and Yelp.

So, you’re looking for the nearest post office? Just tap the record button, say “nearest post office,” and Dragon Go will mark the closest post office on a map, as well as serve up directions.

Another example: Want to see the last “Harry Potter” movie tonight? Open Dragon Go and say, “Harry Potter showtimes” to get movie listings from Fandango, Google, and other online sources.

Of course, there are already several fine search apps for the iPhone that handle voice commands; the mobile Google app, for one, quickly comes to mind.

But the nice thing about Dragon Go is that the app works hand-in-hand with other popular iPhone apps, including Yelp (which offers detailed listings and reviews of local restaurants, stores, and services), Pandora (for free music streaming) and the iPhone’s own music, dialer and mapping apps.

That means you can say “Bruce Springsteen” to quickly listen to The Boss on either Pandora or iTunes, or “call dry cleaners near me” to find out when your shirts will be ready.

In my brief (and decidedly non-scientific) tests, Dragon Go managed to accurately “hear” my questions about … oh, 90 percent of the time, handling request like “Harry Potter showtimes” and “Play Born in the U.S.A.” without skipping a beat.

On the other hand, Dragon Go had a terrible time when I asked for “Zagat ratings on Prime Meats” (a local, very yummy restaurant). “The gap ratings” was one of the translations I got, along with “SIGACT” (the Association for Computing Machinery Special Interest Group—who knew?), before finally settling on the right search phrase.

Still, pretty nice overall—and hey, the price (free) is right.