As MuscleNerd called it, “killer-app.” — It truly is.
Seth couldn’t tell the difference between the 3G FaceTime call and a WiFi FaceTime call; the quality is that good.
1) Jailbreak your iPhone 4 via http://www.jailbreakme.com.
2) Download and upgrade to the latest Cydia package.
3) Open Cydia, Go to Manage then Sources.
4) Click Sources, Edit then add: http://apt.modmyi.com
5) Search for “My3G” — download, and install it.
6) Go through the Rock setup process with a username and password. Open My3G and leave all settings on the default.
7) FaceTime should now work over 3G! — Make sure to “Forget” the WiFi network you are on (via iOS settings) if you want to test it.