Hi,
From my understanding so far it sounded like he wanted a resistor for each piece, so measuring the resistor could tell what the piece was.
For a simple example, say 100 ohms for pawn, 200 for knight, 300 for bishop, 500 for rook, 900 for queen, and 2k for king. So if a piece was on square e2 and the resistance measured 100 ohms, it would have to be a pawn. If that pawn moved to e4 then e2 would have infinite resistance and e4 would have 100 ohms.
But chess moves are not so complex that you would have to track their movement when they are in the 'air', being moved. You only have to track the FROM and TO squares. Adding to that logic, from the start of the game all the piece positions are known in advance, so the only piece that can be on square e2 at the start of a game is a pawn. Thus if on the first move of the game something moves from e2 to e4 it must have been a white pawn.
This will always be true except in the case where non standard chess games are to be played or positions set up that are not from the very beginning of the game. To handle this chess board setup programs have buttons or some other control that allows the user to enter what type of piece they want to place on a given square at the start of the game. For example, the user might select a white queen from the menu, then click the square d5, and that puts a white queen on square d5.
What does have to be tracked in all cases is the FROM and TO squares. The program has to know the square of the piece that is being moved before it moves and after it moves, but nothing else. To accomplish this chess playing machines use momentary push buttons switches under the membrane chess board. The player presses briefly on the square where the piece is sitting, then presses on the square where it is moving to. The program senses the switches which are arranged in a grid, and so it can tell which squares have been pressed. It then follows the action in the program where it changes the arrangement of its virtual chess board, placing the piece on the new 'square' and possibly eliminating the captured piece if there was any. En passant moves are a little more tricky but still the same idea. Pawn promotions mean the player has to press a third switch at the time of promotion so the program knows what piece to replace the pawn with. For example, the player might press e7 and then e8, and then the 'queen' button and that tells the program to make the pawn a queen.
I can see how making the pieces distinguishable through some measurement process could be beneficial, but it may be hard to measure the resistance because that requires a good electrical contact between the board and the piece. Maybe some inductive coupling technique would work better as that would not require electrical contact. It would make the piece design slightly more complex though.