Siri for iDevice!!
Keep in mind, I will not hold or be accounted for any damage caused to your iDevice. This is merely for educational purposes. This is legal thanks to Apple releasing an iPhone 4S firmware with decrypted files.
Requirements:
1.Jailbroken iOS Device tethered (NOT semi-tethered) running the iOS 5.0 or [You must be registered and logged in to see this link.] firmware ([You must be registered and logged in to see this link.]).
2.An iPhone 4S or access to a friends iPhone 4S to obtain 4 unique keys –
assistantID, speechID, validationdata and finally x-ace-host ([You must be registered and logged in to see this link.]).
3.A Siri proxy server.
After you jailbreak your iDevice, Steps can be found here:
[You must be registered and logged in to see this link.]
Note: If you do not have an iPhone 4S, or find it
too complicated to setup a Proxy Server, wait a few days and I am sure
people will release their own 3rd party proxy servers for people to
connect to.
If you would like to learn [You must be registered and logged in to see this link.] install the Spire Cydia tweak to use Siri on your older iPhone, iPod Touch or iPad then you can follow this Spire [You must be registered and logged in to see this link.] guide.

How To Install Spire Cydia Tweak:

Step 1: The first thing you will need to do is [You must be registered and logged in to see this link.] your iPhone, iPod Touch or iPad running the iOS 5.0 or the iOS 5.0.1 firmware.

Note: At this time the Spire Cydia tweak is not compatible with the Semi-Tethered iOS 5/iOS 5.0.1 Jailbreak.

Step 2: Once you have a Jailbroken iDevice running
the iOS 5.0/iOS 5.0.1 firmware you will need to launch Cydia from your
SpringBoard (homescreen).

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Step 3: With Cydia up and running you will need to go into the Search tab and type in: Spire

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Step 4: When you see Spire come up on Cydia’s search
results you will need to click on it, read through the
warnings/descriptions, and then install it to your iPhone, iPod Touch or
iPad.

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Note: The Spire Cydia tweak uses about 100 MB of data, so please connect to Wi-Fi before installing.

Step 5: Once the Spire Cydia tweak has been
installed to your iPhone, iPod Touch or iPad you will need to reboot and
then obviously boot tethered using a Jailbreaking tool like [You must be registered and logged in to see this link.](You can find guide from [You must be registered and logged in to see this link.]).

Step 6: Upon rebooting your iDevice into a usable state you will need to launch the Settings.app and go into the Spire tab.

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Step 7: From the Spire tab in the Settings.app you
will see a text area to enter a Proxy Host. This can be a proxy host
created by you (as explained in the Requirements section at the top of
this how to guide), or a 3rd party proxy host that you have access to.[You must be registered and logged in to see this image.]

Note: As we mentioned previously, if you wait a few
days I am sure people will start to release URL’s to their Proxy Servers
for people to connect to. Please check our Spire Porxy Server list
section by clicking here.

Step 8 ) – With the Spire Cydia tweak now configured properly you
should be able to use Siri on your older iPhone, iPod Touch or iPad.

Congratulations! You have just installed the Spire Cydia tweak to your older iPhone, iPod Touch or iPad.

Agian thanks Ryan Petrich and Chpwn make this happened.
For more information: Please Visit [You must be registered and logged in to see this link.]