Yes, you should be able to do it with QuickTime. The reason that it doesn't record the Video Input overlay is that the recording system is set up to add almost no additional strain to your computer (the last thing you want is to have an audio drop-out because you're recording video to your hard-drive, or using too much CPU). Perhaps I will add an option to record this in a future version. It's hard to say what would be the best way to do this though, as most video camera's input full HD video - and encoding that in realtime is going to put quite a strain on the computer.
