Recording sound and video is a little more complicatet than playing it back, as you would probably expect, but it is still fairly simple. There is just a little more setup to do. Have a look here for the whole media-stuff.
There already is a CameraPreview-Example provided by Google itself: (click)
but as long there is no way to associate an usb-camera with the emulator or test on an actual device it is not that useful.