Have you looked at the Apple Last Resort font? Knowing from what character block an unsupported character comes is handy, but I wouldn't equate a little box with a picture and a Unicode range name with actually displaying, however poorly, a specific character.
It's better than not knowing what range the thing is in. It helps the user know he has received, say, Telugu data or whatever.
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Michael Everson * * Everson Typography * * http://www.evertype.com
