Voice Control, the function that allows us to do different tasks using voice commands on any iPhone 3GS/4, iPad, iPod Touch 3G/4G, is available starting with iOS 4.2.1 directly from the lockscreen. Basically lock the phone, hold down the Home button for a few seconds and the Voice Control screen will appear automatically. In previous versions of iOS, Voice Control only worked if the phone was unlocked, but Apple thought it would be useful to have this function even when the phone is locked.
Unfortunately, the function is only available for the 5 devices mentioned above, and I don't know how useful it is for you, but I haven't used it more than 4-5 times since I have an iPhone 3GS/4 . Apple made this function especially for certain languages of international circulation, but since Romanian is not among them, the application does not respond at all to commands in Romanian and quite difficult to those in English.
UPDATED: It seems that I was wrong, Voice Control also works on 4.1 from the lockscreen.
