Currently live video feeds from cameras can be used in MixEmergency through either the 'live feed' hidden feature (mentioned on this forum), or through the use of Quartz Compositions. I'm not familiar with the show xpress video capture card. If it is available to QuickTime as a recording source, then it should also be able to be used with MixEmergency. Are you wanting to use any input as a live feed (e.g. tv, output of another computer, etc), or just a live feed from a camera?