I offer to you my take on the which hand plot, it uses two spectators and you are able to predict whether the first spectator flips heads or tails with no questions asked. Then spectator two is asked to place both hands behind his back and switch the coin as many times as he likes. He is then asked to just think HEADS or TAILS.
You are able to predict the outcome, telling him what he is thinking, and what hand the coin is in, and prove it by showing your prediction which has been on the table since the beginning. Best of all it uses no special coins, no electronics and only one business card.