In fact, this kind of card can be used in performing various kinds of card-magic. First you can give an envelope to your audience and tell them that this is a prediction. Later, ask them to choose one card at random from the deck and sign on it, then put it back in the deck. Next, open the envelope yourself and are surprised to find that it is a condom. At this moment, you need to slightly shake this condom and it will magically change into a card immediately. Most importantly, this magic card is exactly the one your audience just signed. It is going be the most fantastic magic you have ever seen and you deserve to have it.
Easy to do