UPDATE: This is a feature on the iPhone 4s
On this picture there is a iOS screen with a keyboard and a new button. This button looks like it will allow you to talk into the iOS device and it will turn it into speech. This is just like what Android has and the icon looks the same as well. But this may only be for the new iPhone 4s or iPhone 5.
The system will actually speak back and forth with the user to gain the most information in order to provide the best results. The user essentially can hold a conversation with their iPhone like it is another human being. For example, if a user is making a meeting with me, they will say “setup meeting with Mark” and the first “bubble” of the conversation thread will say that. After that, the system will speak back: “which e-mail address should Mark be notified at, work or personal?” This question will both be spoken out loud by the iPhone Assistant and shown as a new “bubble” in the conversation thread. The user will then respond with the email address they want to notify me at, and the appointment will be made. The iPhone will even show a quick glance at a calendar view to confirm the appointment. If the Assistant was sending an SMS, as another example, a mini SMS view would appear so the user has a quick glance at the SMS thread.