Can this be done?

A friend is building a house soon and we are exploring something that sounds easy but everyone says is impossible.
He wants a centrally located media center with (a server I guess) with dvds, music, home videos and the like that can be retrieved from any tv/monitor in the house.
This way a person in one room could be watching tv or a video while another could be doing something different in another room.
We ask and found out that the Media Center Extenders are only one way devices.
Also, every tv has it's own cable box so we don't know how this comes in.
Would it take a full media center computer in each room or are there other devices that would do this?
Just as a note, he was thinking about rather than hanging a picture when you walk into the entry, have a monitor on the wall slideshowing familt pictures.
Sounds fun huh?