A long time ago a fellow made an addon that make a chat bubble above a player’s head when he/she is typing. You can see what he/she is typing on the bubble. It was once on garrysmod.org but itgot deleted. It’s really fun and funny. It’d be gr8 if some1 made it.
http://www.facepunch.com/showthread.php?t=669670 is similar to what you want, but without text.