@accessranganath: Advice: NEVER publicly display your original name and other contact details on the internet!
As for the topic,(correct me if I'm wrong
) I remember an episode from a show on National Geographic known as "I Didn't Know That!". The episode had shown a spy gadget used to capture sonic waves to eavesdrop on conversations. They had proved clearly that the gun was as big as a sniper rifle and needed the correct orientation to capture decipherable waves. Doesn't this work on the same principle?
If so, then it would be very difficult to exactly find out what is being typed as it was difficult to decipher the contents on the show too. So that "fully or partially decipher" should be "partially and sometimes fully decipher".
Another gadget for the Bond guy!
@NIGHTMARE: (Offtopic) Nice profile picture! beats mine. Gotta get image searching again!