Mobile app writer Steve Troughton-Smith successfully created a fully functional implementation of Siri working on both the iPhone 4 and the fourth-generation iPod touch. It’s not a new fact that the Siri UI can be run on non-4S hardware. The real magic happens when Siri is able to talk back to you
As you can see in the above videos, Steven and Grant have been able to get Siri connecting with Apple’s server. Performance is smooth and Siri responds very quickly. The first public evidence for a Siri port to the iPhone 4 was posted by Steve Troughton-Smith weeks ago in conjunction with Mark Gurman of 9to5Mac. Unfortunately there is no release of these to the public, this is the sad thing, anyways hope to see it soon.
Here 9to5mac demonstrates in the below video the comparison between iPhone 4s & iPhone 4