I got a response from Elgato about why a HD video input is unlikely. I thought I'd post it because the question gets asked quite frequently.
Richard,
Thank you for contacting Elgato Systems.
No consumer products for the Mac or Windows can bring HDTV from component, DVI or HDMI to your computer's display and hard drive.
USB 2.0 or FireWire is not the limiting factor. The lack of affordable chipsets to achieve this is one factor. The desire of the cable and satellite industry to prevent their signals from reaching a computer's hard drive is another.
Thus, this is a ways off, perhaps a few years.
You can bring in analog video using composite or S-Video, but not digital using component, DVI, VGA or HDMI.
Nick Freeman
Customer Support
Elgato Systems LLC