We'll call this a mid-level difficulty hack we know many are interested on. One of those really cool iPhone 4 features that we wish wasn't restricted is FaceTime calls being limited through Wi-Fi. It sort of becomes pointless to have such a feature and not be able to use it in every scenario thinkable. Well, for those of you who've already taken the Jailbreak plunge, you'll be happy to know there's a way to get it working with a little help from Cydia.
As it turns out, the Jailbreak doesn't really liberate FaceTime to work through 3G form the start, but Cydia offers an app called My3G which tricks the phone into thinking it's got Wi-Fi when it's really connected through 3G. The result is having FaceTime work implicitly through 3G because the phone thinks it's using Wi-Fi once My3G is running. Here are the steps to get it working:
1) Jailbreak your iPhone 4 via 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.
See Apple.. That wasn't so hard! Here's a short video of it working: