I think hypersonic sound will be one of the most exciting technologies for 2004. Speakers that emit sound like a torch does light. You can point and shoot sound to a single person in a crowd and only they can hear it. Might not be the most practical technology but is certainly very cool and would be great for fucking with peoples heads, eg. x girlfriends etc.
http://www.atcsd.com/tl_hss.html