This day can’t get any better than this, first an untethered Jailbreak was released for iOS 5.0.1 and now after such a long time, the most awaited Siri port is now possilbe legally through a tool called “Spire” availalble to install from Cydia on y0ur iOS device.
Chpwn :-
Spire is my (along with Ryan Petrich) new tool for installing Siri on previously unsupported, but jailbroken, devices. Spire is a small download, but while installing it will download Siri itself (directly from Apple). Spire is available in Cydia right now — go get it!This will use about 100 MB of data, so please connect to Wi-Fi before installing.
However, Spire is not a complete solution. Apple still requires authorization to use Siri, so information from an iPhone 4S is still required. To insert this information, Spire allows you to enter your own proxy server address. I’ve put up a list of my ideas on how you might get access to a proxy; hopefully you can figure something out.
Spire uses a new method to obtain the files necessary for Siri, so it doesn’t have thecopyright issues encountered by previous attempts. Similarly, rather than directing all traffic through a specific proxy server (and the associated privacy issues), Spire allows you to specify your own proxy server.
Spire Installs in your Settings app and you can activate the Siri GUI by navigating to Setting > General > Siri after you have set up your proxy server.
You need a jailbroken device to get this tool installed on your device and this those who have Semitethered jailbreak device, the tool is reported to not work very well. So install this tool on a properly jailbroken device.
For more info, Chpwn has provided an FAQ page on which you can get further assistance.
Installed Siri on 3gs and iPhone 4! Tested and Working