I should have done some Googling before I asked about the
telectroscope.  The real device is apparently as fascinating a piece
of technological fiction as anything Twain might have written about
its inventor!  http://en.wikipedia.org/wiki/Telectroscope

However, the idea did not die with Jan Szcsepanik.  It was finally
brought to fruition just last year in a breakthrough (in more than
one sense of the word) that should have received more general
recognition than it has.  Here's the full report:
http://www.telectroscope.net/ Be sure to read all the links...

(Next I have a bridge in London to sell you).