I realize most presenters prefer using their own laptop and presentation trigger but the best and simplest way to do this is to use your own computer with an HD-SDI or HD-Component video output that you can feed into an HD capture device in your Catalyst.
I have Decklink HD cards in a few of the Catalyst machines I use which have HD-SDI inputs. So I just built a little micro PC with an HD-SDI output card. This is the solution most TV crews use for feeding in Powerpoint to their switcher. In this case, it's just Catalyst instead.