The assistant feature of iOS will greatly improve when iOS5 launches. The speech control function will be activated by holding the home button for a few seconds. After that a new array of options is available, activated by speech, according to the website 9to5mac who claims to have an early version of the iPhone 5 in their possession.
The new assistant allows the user to open the message center and to use speech in order to ‘write’ a text message. The phone automatically converts your speech to text. In addition you can add agenda points or start the navigation app. One of the new features includes asking where a certain contact is at that time. This function can be disabled. The phone is also able to talk back at you. It can ask for extra information, like to which email address a certain message needs to be sent.
Another new function is Wolfram Alpha. This lets you ask any question and the phone will try to answer it. This can be for example a scientific question or something on the field of mathematics. The phone answers verbally.
The Assistant feature seems to be rather similar to the Android voice function. In Android accessing features like these verbally was already possible.