How do I capture video in real time from a Canon 5D Mark II to iMac in Final Cut Pro?
You may be able to use the Log and Capture window (File>Log and Transfer):


However, this requires you to hook up the camera in such a way that Final Cut Pro recognizes. IIRC, the Canon 5D Mark II doesn't have a Firewire cable. The HDMI capture card might work, as long as FCP recognizes it.