iDeviceTrickz have released a new Siri proxy and server that will work for free on your jailbroken iPhone 4 and iPod Touch 4G.
To install it:
1. Open Cydia
2. Install Spire from the Big Boss repo
3. Open Settings on your iDevice
4. Look for Spire
5. Copy and paste https://76.74.219.178/
6. Open here on Safari
7. It will re-direct you to Settings
8. Install the certificate
9. In Settings, go to General and look for Siri
10. Enable Siri (button will be blue)
Now you can enjoy Siri on your iPhone 4 or iPod Touch 4G.
EPELTECH 