Hackers have been attempting to port Siri onto hardware besides the iPhone 4S ever since it launched, and now jailbroken iPhone 4 or iPod touch users can get in on the fun. A Chinese hacker group known as CD-Team released the H1Siri application to Cydia (the main app source for jailbroken iOS devices) and now dozens of users have taken to YouTube showing Apple's digital assistant running on their unsupported hardware. You need to run iOS 5 or higher and have a jailbroken iPhone 4 or 4th generation iPod touch to get Siri working, but installing is a fairly straightforward process if your device meets these requirements.
While the installation process may be uncomplicated, H1Siri isn't working flawlessly yet. A number of users are reporting consistent errors when accessing Siri, and installing this app apparently can break camera functionality (though fixes are out there for those who need them). There's also the potential for errors when installing the custom repositories in Cydia necessary to install this app, thanks to high amounts of traffic hitting the various servers hosting the files. Due to these issues, H1Siri currently feels like a fun hack for the curious, but not something users should count on as a reliable tool.
Update: It sounds like there might be more reasons to stay away from H1Siri than just instability. Developer Grant Paul, who was one of two people behind a port of Siri to the iPhone 4 and iPod touch in late October, believes that H1Siri is using a proxy server, and that any information that goes through Siri is being transmitted to a potentially insecure third party — this could inclue SMS messages, calendar entries, contacts, and even location data. Paul's planning to release more info on his concerns with H1Siri soon.
Update 2: Grant Paul's given us the whole scoop on how H1Siri works and why this insecure hack is likely not long for this world. According to Paul, Siri uses a cryptographic "token" that uniquely identifies an iPhone 4S. This token can't be faked; it is generated daily from your iPhone 4S' serial number. The H1Siri hack involves funneling Siri requests through a server and then adding a token from an iPhone 4S there. Due to this, all of your H1Siri requests and associated data are funneled through CD-Team's servers. Since Apple issues these tokens, they can block it at any time and we wouldn't be surprised for Apple to block H1Siri soon — even if they don't, we'd advise readers to steer clear of this hack.