Siri, the 'digital assistant', that Apple bundles with the iPhone 4S, has been hacked to work on earlier Apple devices including the iPhone 4 and iPod Touch.
iPhone hacker Steven Troughton-Smith demonstrated the ported Siri in a video, adding that Siri was completely functional on the iPhone 4 despite the single core processor. The port to the iPod is said to function but the iPod's poor microphone hampers the usefulness.
Sadly the hack itself is quick involved and requires a jailbroken iPhone 4S and files which the hackers aren't free to distribute so they wouldn't say when or if it would be made available.
PCR has more details on this story.