From the same source as this possible leak comes a few shots of what could be video chat on the iPhone. Who knows. UPDATE: This image is fake.
But, supposing it's real, it's interesting to note that it appears to be on Wi-Fi. It's possible that it's like Skype and SlingPlayer and only work over Wi-Fi. On the other hand, we can't make that conclusion yet, but since video chat is a "data" service, it makes sense that it goes over whatever "data" service you're currently on (Wi-Fi or 3G). And it may be a simple photoshop anyway—just load and image, then add the green light in Photoshop (as shown here). In any case, remember to check out our liveblog on Monday to see the real iPhone reveal. [Nowhereelse—thanks Brendan]