If you already have an iPhone 4, there are only really two things worth upgrading to the iPhone 4S for: the improved camera and Siri. But hopefully soon we might be able to cross one of those things off the list.
Steven Troughton-Smith has successfully ported over the Siri interface to the older, not as blessed, iPhone 4. Performance was initially pretty terrible due to a missing GPU driver, but that has since been corrected and it runs just fine, as seen in the video below.
Update: I’m an idiot and embedded the wrong video. That was the first one, with the terrible performance. This is the correct one. I apologize for my uselessness.
There is one problem though… it doesn’t actually do anything. Like I already mentioned, this is just the interface, not the actual service itself. Siri works by taking your voice input and sending it back to Apple’s servers, where all the real data crunching happens. Naturally though, they’re only authenticating requests sent by actual 4S hardware. So until either Apple enables the iPhone 4 specifically or someone figures out a way to spoof the identification, this is nothing more than an extra menu option. Still, it’s an interesting development and hopeful step in the right direction for us iPhone 4 owners stuck in the third world.