Both of these applications allow a spectator to think of a card, then your psychic friend reveals it on an answering machine. Requires an Apple device (iPhone, iPod Touch, iPad) for either.
If I only had money to buy ONE, I'd choose iPredict because:
1) Can use the spec's phone
2) Comes with 35 minutes of video instruction
3) Has a business card template you can print out
4) Spec can watch your phone the entire time
But realistically, you can buy both for $8 so just do it ...