What would be an appropriate sensor to use with arduino lilypad to detect movement of card. The sensor will be attached to one side(top) of the card, when the card is flipped i.e when sensor faces down, then I should be able to detect it. Please help. The card would be held in hand just like a visiting card( a bit thick ). Imagine reading 1 side of card then we turn it other side to view more. So I must know if the user has turned over the card.