Update per Engadget.com: We’re told this isn’t actually the Sam Mendes video calling ad, but rather an Apple promo video produced internally. We’ll just have to wait and see if Mendes can top these heartwrenching images of American beauty with his ad.

Steve Jobs, the visionary behind Apple’s magic gadgets, descended on San Francisco today to introduce the iPhone 4 to press and technology geeks at the Worldwide Developers Conference 2010.

As everyone cheered for Jobs and his interactive presentation, including a sneak peak at iMovie for the iPhone — the phone will be able to shoot in 720p HD video, which can then be edited in the new app — and front-camera video chatting through the use of “FaceTime.”

Allowing users to video chat via WiFi is a feature many people knew was in the pipeline, so its introduction wasn’t a major revelation, however, along with the feature demonstration was the premiere of a video commercial that director Sam Mendes created for Apple.

Mendes, the Hollywood director behind the cult-classic “American Beauty” and Broadway’s revival of “Cabaret,” helmed a spot for the iPhone 4 and used some touching scenarios to show how powerful “FaceTime” is. With Louis Armstrong playing in the background, the Mendes commercial shows a father chatting with his wife and baby, a mother-to-be broadcasting a sonogram to her military husband and a deaf couple using sign language. Cue the heartstrings.

Enjoy the commercial: