“Siri one of the mosted talked about features on the new iPhone 4S lets you use your voice to send messages, schedule meetings, place phone calls, and more. Siri being purely software has limited this feature to the iPhone 4S. Other supported devices are able to upgrade to iOS 5, but Siri will not be included in the upgrade but as we know anything is possible or hackable for some of us and this day has came.
Developer Steve Troughton-Smith has managed to get Siri to run on iPhone 4 and fourth generation iPod Touch (uses the same A4 chip as iPhone 4, but has only 256MB of RAM). Throughton-Smith says Siri runs just as fast and smooth on the iPhone 4 as it does the iPhone 4S. The iPod Touch has some problems due to the inferior microphone (iPod Touch wasn’t designed for calling like iPhone), requiring you to talk very loudly but the actual Siri software runs flawlessly. Below is a video of Siri running on the iPod Touch.
Owners of iPhone 4 and iPod Touch 4G shouldn’t get too excited though, as Troughton-Smith says a public release should not be expected anytime soon. There may also be legal issues of distributing Apple’s code, making a public release impossible