Apple CEO Steve Jobs announced a new video calling service called FaceTime for the company's new iPhone 4, during the World Wide Developers Conference in Cupertino, California today.

The new iPhone 4 is 24 percent slimmer than the iPhone 3GS, according to Jobs, but its most striking hardware upgrade is an additional camera -- one on the front and one on the back. Both cameras can be used for FaceTime calls.

For now, FaceTime only works over WiFi networks and between two iPhone 4 devices. Jobs said the WiFi situation will likely stay the same through 2010, but that Apple needs to "work with" the carriers to change the WiFi-only situation in the coming year.

During a demo video, Jobs showed various use cases for FaceTime, including one that showed two people using sign language to communicate via a video call.

Interestingly, Jobs said that FaceTime was based on "an open industry standard," which might mean there is an opportunity for healthcare app developers to find ways to build on the service and add healthcare specific features in the future.

"You know I grew up with the Jetsons... and video calls," Jobs said during his keynote, according to a report over at Engadget. "And now it's real."