You are talking about Voice Control for music. It has been a feature for a while. For the User Guide:
Voice Control
Voice Control (iPod touch 3rd generation or later) lets you control music playback using voice
commands. To use Voice Control with iPod touch 3rd generation, you need Apple Earphones with
Remote and Mic, or a compatible accessory with a microphone.
François J. Perreault wrote:
I have an iPod touch 4th Gen. with the latest iOS 5 and if I hold the Home button for a bit there's a (new) voice command thingy that activates and tries to guess what I want from what I say.
Most of the time if seems to think I wanna play music though. 🙂