Shortly after the release of iPhone 4S developer Steven Troughton-Smith managed to install the virtual assistant on his iPhone 4, though at the time one very important feature was not available - it was not able to talk to Apple's servers, 9to5Mac (opens in new tab) reports.
Now the hack is complete but, as Troughton-Smith describes, the process was not easy: "It does require files from an iPhone 4S which aren't ours to distribute, and it also requires a validation token from the iPhone 4S that has to be pulled live from a jailbroken iPhone 4S. It's about a 20-step process right now."
However, after all his efforts Siri is apparently working on the iPhone 4 with 100% functionality. Troughton-Smith posted a short YouTube video showing the two Siris working side-by-side, with the older handset appearing to be just marginally slower.
The developer also attempted to port Siri on a fourth generation iPod but here the hardware was not nearly as attuned with the new technology. The microphone was the main culprit for spoiling the Siri experience on an iPod; Siri doesn't answer questions properly and the user needs to speak very loudly and clearly to get any reaction.
It should be noted that Apple recommends you do not hack your iPhone, iPod or iPad, and doing so will invalidate your user warranty.