The iPhone 4 jailbreak have now been made public and so the My3G app has been updated for the iPhone 4 and is now available in the Cydia store. With this app, you could use facetime over 3G on iPhone 4. You could get the Facetime video call feature in 3G speed with this app.
– In-App popup request to enable/never ask for My3G to be enabled for that app
– In-App indicator when My3G changes the network from 3G to WiFi
– Ability to select which apps are My3G enabled and not.
– Default Apps â€“ no configuration for the most popular apps!
– SBSettings Toggle! You can temporarily enable My3G for all apps or toggle back using your defined Apps list
– Dynamic enablement â€“ Higher successs rate (near 100%) then 3G Unrestrictor (which does one off solutions for apps). My3G enables 3G indicators more dynamically.
The My3G app is available for a cheap price of $3.99 in the Cydia store. If you haven’t jailbroken your iPhone 4, then follow the guide given here to get Cydia on your phone and use Facetime over 3G network.