DVI (HDMI) capture can be achieved by using a Decklink Intensity or Intensity PRO capture card. It will accept resolutions up to 1080i (not 1080p)
http://www.blackmagic-design.com/products/intensity/
Cards are relatively in-expensive. 2 cards can be used in a MacPro at the same time. Frame delay is normally 1-2 frames - but the cards do frame buffer - which is un-controllable.

Phoenix card will support 2 x SD-SDI or 1 x HD-SDI in a 2008 MacPro. Untested in New 2009 MacPro. Frame delay is 1 frame. A more expensive option than the Intensity Card.

Not tested the Canopus Twinpact100 - watch out for latency on firewire

Beware of frame delay in camera processing equipment and in processing before it gets to catalyst - and again between catalyst and projectors....

Simon