To make it work, you'll need a jailbroken iPhone 4 and the Cydia app. Once you've added apps.iphoneislam.com to Cydia, grab FaceTime Hacktivator. From there, you should be good to go.
Keep in mind that you jailbreak your iPhone at your own risk. If you're comfortable with that process and adding apps via Cydia, then have at it.
[Via The Mac Observer]