Here's the idea: Chess rules are all exactly the same with the same pieces and everything EXCEPT that you can't see your opponents pieces unless they are in your "line of sight".  The line of sight would include anything that you would be able to take or anywhere you would be able to move. For example: A pawn would be able to see a piece directly in front of him and the pieces diagonally in front where he could take.  If the white g pawn was on his home square and there was a black piece was on g3 and another on g4 then, unless white could see through a different pieces line of sight, white would only be able to see the piece on g3 because the piece on g3 is blocking the pawn's line of sight to the g4 piece.  Also because there is this idea of fog of war players will not have to declare check and as such will not have to move out of check.  For obvious reasons this variation would have to be done online, but I think that this is an interesting variation that would change the way you play COMPLETELY!

Btw, I thought of this on my own. Since then I looked it up and there was a similar(not exactly the same) version that was already made that you can download and play.  Just wanted to say that.