(adsbygoogle = window.adsbygoogle || []).push({}); First things first, you will end up using a proxy for siri so do not do this if you do not want to use a proxy for siri.
Ok So You need a tethered iDevice on 5.1 (I have an iPhone 4) which is the only device I have tested thus far.
Go to Cydia and add a source.
First add, repo.technetec.com
Secondly add, repo.technetec.com/vip
Install spite 2.3 (for iOS 5.1)
Next when it asks to reboot EXIT CYDIA BY DOUBLE TAPPING HOME AND HITTING HOME AGAIN!
Then hold power and turn off iPhone by sliding to power down.
Go to redsnow and boot in tethered mode by entering DFU mode. (instructions in redsnow)
After it has rebooted in tethered mode, your siri should be ready.
All you need to do now is set up a proxy server with siri.
To install the fix 2.4, install it and exit cydia the same way. Then boot into tethered and you are set!
Happy Jailbreaking!
italianbeast007
MOD PLEASE MOVE TO IOS DEVICE MODS PLEASE

This will put your iDevice into the state(I forget what its called) where it just boots up over and over again, making your device unusable.

im just waiting for the ipad 3 jb

[ATTACH=CONFIG]16526[/ATTACH]
Working fine for me....
You just have to exit cydia and restart by sliding to power down. Then boot into DFU mode and use redsnow to boot into tethered mode.

I got the state you were talking about the first time because I rebooted from cydia instead of the way mentioned above