I love a good trick, and it's been ages since I've reviewed any iPhone-based magic, so with the weekend coming up, here's a suggestion for something to keep your friends guessing. The trick is called Mental Killer, and it's just that.
Basically, here's the effect: you place a note with a phone number of a friend on the table in full view. You have someone select a card, or if you don't have a deck nearby, they can just name one at random. Let's say the four of diamonds was selected -- the friend's phone number is then dialed and verified to match the written number, and your assistant will hear a voice mail message from your friend that names the card. Whoa!
It's a slick variation on a trick most magicians will understand. If you have a few people standing around you can have the spectator put the call on speaker phone. I've tried the trick on a few friends, and it was definitely a fooler. The trick can be repeated with another card named, but I think it dilutes the impact -- just do it once and leave 'em guessing. The app was originally $20, but since it's on sale for just US$0.99, you can get a good price for such a grand effect. Check out YouTube to see the act performed live.