The problem with using an iPhone (or iTouch) to perform a magic trick is that the sophisticated electronic gadget appears to do all of the work, even when it isn't. Although a magician may need to master and apply sleights in the course of performing an iPhone magic trick, the iPhone gets the credit.
Worse, when the iPhone steals credit for a magic trick, the magician is held in lesser regard. The implication is, anyone with an iPhone and the magic app can do the trick. It's the old assumption that the only things that separates magicians from lay people are secrets and magic props. And this can't be further from the truth.
One more consideration, when you employ an iPhone in your magic, what theme can you use beyond "technology?" By employing a "technology" theme, I maintain that you're supporting the notion that the iPhone is doing the work.
In the Know?
Of course, simply knowing a secret or owning a magic prop does not make a magician. Beyond secrets, a successful magician has to possess magic skills, and abilities to connect with spectators, command attention and entertain, which definitely separates magicians from lay people.
So while some iPhone magic apps do incorporate clever ideas and handlings, I have yet to come across one that qualifies as the type of magic that I want to present at my shows and gigs. I want my magic to be respected for my skills, character, presentation and entertainment value, and not because I happen to own an iPhone.