Consisting of a send unit, a receive unit, a 5V power supply, and a pair of Cat-5 cables up to150' long, the "ex-tend-it" HDTV Extender could be a godsend for those who would like to put their source components at one end of the room and their display or projector at the other end. It's an especially good solution for difficult wiring circumstances, where line-of-sight distance might not be excessive but the cabling needs to traverse walls, ceiling, and/or floors.
The send unit of the HDTV extender accepts a DVI/HDMI input and transmits the data via Cat-5 to a receive unit near your display. The Cat-5 cable carries digital data and control signals to the display over surprisingly long distances.
The HDTV Extender is claimed to be HDCP (high definition content protection) compliant. Gefen specifies a video bandwidth of 1.65GHz, and says the Extender supports "480P, 720P, 1080I, 1080P and 1920 x 1200 resolution." Power consumption is a mere 15 watts max and shipping weight is only 3 lbs. For even longer runs, Gefen makes a similar device that transmits DVI/HDMI signals over fiber optic cable. More information here and here.