This is just my opinion so please don't take this personal. Why would you ever do a trick that it so obvious how it is done? The spectator will never ever believe that their card was ever in your phone. The method is so clearly an app that no one, even my grandma (God rest her soul) who's never even seen an iphone would believe that.
Instead of trying to find that app, get a good book on magic and learn something that will actually entertain and possibly fool someone.
Again, this is all just the opinion of some dude, so don't take this as an attack on you.
Just because YOU
couldn't trick someone with an iphone app does not mean the OP can't either.
According to your theory, why would any spectator ever believe any card trick ever? After all everyone knows
cards are used as the medium for a performer
to perform a trick
. Everyone knows
magic is taking place, and this is especially reinforced as soon as a deck of cards comes out, as a deck of cards have been synonymous with magic performance
since the beginning of time. That being said I would argue that a trick which includes transferring the hero's card 'into' and 'out of' an iphone would add MORE
of that 'actual
magic' feel to it then without.