With an update that hit the app store yesterday, you can now talk to Pocket Universe, using Siri speech recognition by tapping on the microphone icon on the built-in keyboard. You can say things like "Where is Jupiter?" or "What is the phase of the moon?" and so forth.
I tried several queries like, "What time does Mars rise?" and "Find M42 in Orion." It all worked very well, and certainly beats typing in a dark backyard. If the app needs to talk back to you, it does so in a synthesized voice. The voice quality is a little rough, but it's slated to be improved.
Author John Kennedy says he hopes to add voice-driven weather forecasts and other astronomical tidbits soon. Without the new voice commands, the app has a lot of features, including a 10,000 star catalog, as well as lots of deep sky objects. You can track the International Space Station and contains updated news sections and links to topics via Wikipedia.
If you have the app, you'll get a free update with the voice functionality. If not, the app is US$2.99 and well worth it. Pocket Universe requires iOS4.2 or later and is a 43 MB download.