Siri has been making her rounds through non Apple iPhone 4S devices as of late, after being ported to the Apple iPhone 4 it has now also been ported to the Apple iPhone 3GS. Apple has made us believe that Siri requires the advanced hardware of the iPhone 4S in order to work, but the demonstration video shows it working quite well on the iPhone 3GS.Apple has used the Siri voice assistant to push iPhone 4S sales, but recent rumors point towards the service making it's way to the iPhone 4. While we are not sure if the service will make it's way to the older iPhones while Apple is still selling the new model so vigorously, there is hope that we may see the service on the iPhone 4 in the future.
Meanwhile take a look at Siri running on the iPhone 3GS.
source - Smash iPhone