1)
umm I mean you do have an 8x8 grid (8 bits each row) and you could have pieces make up bits being on or off and make a 8 letter phrase (each row being it's own letter).
(Ascii Wikipedia for your reference - https://en.wikipedia.org/wiki/ASCII#ASCII_printable_code_cha...)
2)
Maybe you could also do something like the Where Am I Game?
example:
I stay one night in Denver; four nights in San Francisco; And one night in Washington DC;
Where am I?
1 Denver = D 4 SanFrancisco = F 1 WashingtonDC = W
(DFW) -> Dallas
So you could do something like playing a chess game and for every attempted move (like player 1 moves a Rook but keeps his hand on it and taps the board thinking about the move and then places it down means the letter 'o').
3)
There was also a movie with Bruce Willis (or The Rock Johnson. I always get them confused). Where the main guy tries to escape from a space prison. There was one scene where they communicated over a chess game by only talking when there hand was on the queen. Any word spoken while on the queen was then concatenated to a sentance to convey what they were really talking about.