Since the debut of Siri virtual assistance alongside the iPhone 4S, hackers have been trying hardly to port the feature to older iDevices. There are no hardware limitations but the only concern still that the service needs to connect to Apple servers to get it working.
Siri’s dictation feature has now been made publicly available in Cydia for the iPhone 4, 3GS, Touch 4G and it actually works. Developer Eric Day has released a jailbreak tweak called Siri0us.
“Siri dictation for your iOS 5 devices. No iPhone 4S keys/files required.”
The tweak actually works but sadly with some Ads around.
Add the source http://apt.if0rce.com on Cydia to get the tweak