I do a lot of things with my phone such as iForce by Greg Rostami, iPhone Calculator Prediction which Dynamo performed on his TV special, and Cell by David Stone. I believe magic with our phones should only be limited to what our spectators are familiar with such as the calculator app and something that isn't too out of the ordinary such as the doodle app which is incorporated into iForce. Apps specifically made for a magic routine such as Chris Kenner's Rising Card app (which is good!) can push the idea of some form of gimmicky trickery onto our spectators because it's specifically tailored for a magic trick which the spectators can clearly see. So what I'm trying to argue here is that magic with your cellphone can be awesome because it fits right in your pocket and you won't leave the house without it. But I believe routines with cellphones are only strong depending on what you choose to do with them. If you decide to download cheesy magic trick apps anyone can get on the app store or the android market, no one will be impressed let alone be fooled. But if the trickery mechanics behind the trick hide in plain sight, almost like sleight of hand, can leave a lasting impression on the spectator because your doing the magic with something organic instead of a pack of cards.
With this said, magic involving my phone have been proven to me as true crowd pleasers which have been friendly to me, the magician as my phone fits in my pocket and I can do routines with it right on the spot if someone asks me to do a trick and I don't have anything else on me (which nearly every magician has experienced once now and again)