WWDC: Video Calling on iPhone 4 With FaceTime: Wi-Fi Only

We already knew that iPhone 4 would have a front-facing camera, but Steve Jobs waited until the end of his presentation to actually show it off. Using his traditional “one more thing” schtick, Jobs called Apple (s aapl) designer Jonathan Ives using FaceTime, a new software application for video calling on the handset. But first, Jobs asked the audience to turn off their Wi-Fi devices. Why? The new feature works between iPhone 4 devices and only over Wi-Fi, which is good and bad.

While bandwidth-intensive video won’t eat up cellular data plans since it uses Wi-Fi, this constraint does limit the potential locations to use FaceTime. Apple says it “needs to work with cellular providers” for video over 3G, but it had better hurry: More than 30 billion video calls are expected by 2015, according to our latest GigaOM Pro report (subscription required). Regardless of the connectivity challenge, Apple is making use of both cameras on the new iPhone 4 — users can show their face with the front camera or switch to the rear camera to show off the world around them.