A recently released Siri port called Spire promises to bring Apple's personal digital assistant to any jailbroken device running iOS 5. And unlike previous Siri ports, Spire is not burdened by copyright issues, according to its developer. But as is typical for hacks that put Siri on non-Apple approved devices, Spire is not a complete solution and there a few technological hurdles to overcome. Besides a jailbroken iOS device, you also need access to an iPhone 4S and a proxy server as a go-between for your jailbroken device and Apple's servers.
Spire comes from Grant Paul (no relation to the author) who recently worked with Steve Troughton-Smith to get Siri running on the iPhone 4 and helped created an iPad 2 jailbreak method in July.
A token iPhone 4S
The downside of porting Siri to devices other than the iPhone 4S is that they require an authentication token from Apple's latest smartphone, currently the only Apple-approved Siri device. Most of Siri's voice-command processing happens via Apple's servers instead of on the actual device. To prevent unauthorized use, Apple requires each Siri-enabled device to have an authentication token before it can communicate with Apple.
Thus Spire will only work if you have access to an iPhone 4S to get your authentication token, and then you need all commands to go through that proxy server. That seems like a lot of technical overhead just to get a few voice commands on your phone, but right now it appears to be the only viable solution.
Other hacks, including the H1Siri hack that came out in early December also require a proxy server. The advantage with Spire, however, is that you can configure your own proxy instead of using a third party. Using your own server is a much safer way to handle a Siri hack since it avoids having your personal data flow through a server that you may not be able to trust.
Another advantage Spire has is that it appears to be a "legal" Siri hack, or at least a piracy-free one. “Spire uses a new method to obtain the files necessary for Siri, so it doesn’t have the copyright issues encountered by previous attempts,” Paul recently told 9-to-5 Mac. Earlier in December, Apple released an iPhone 4S update that allowed hackers to obtain iPhone system files without resorting to piracy. You can download Spire for free from the Cydia market for jailbroken iOS devices, but you'll want to be connected to a Wi-Fi network when you do it as the app download requires 100MB of data. You can also find a tutorial on how to install Spire on the blog Limera1n.
If you're thinking of jailbreaking your iOS 5 device, the iPhone Dev Team announced Tuesday morning that an untethered jailbreak for devices running iOS 5.0.1 (not including the iPhone 4S and iPad 2) was now available.