Here's a list of the features such a device should have:
http://www.cadsoft.de/vdr/hdtv-dream.htm
Please let me know what you think about this, and if I have forgotten anything or got something wrong.
I feel that component video output is missing. It is capable of outputting HDTV signals, and many consumer devices have component inputs. I think Scart isn't specified for HDTV bandwidth, so TV's don't accept such signals from it.
Of course DVI/HDCP/HDMI out runs component outputs in quality, and there probably are some relatively cheap converters from DVI to component.
Regards, Jori