Siri on the iPhone 4, iPod 4g, and sometimes the iPhone 3Gs
New tweak in Cydia called Siri0us can be downloaded from the repo:
This app is a mod for your iPhone to bring Siri to unsupported devices. The developer pulled the app for legal reasons but you you can still dowload it from the above repo and the deb file from here:
This app doesn’t work on iPhone 3GS’s with the old bootrom, so sorry.