There's a trick I've learned that has come in quite handy when I've come across screw's with strange tip's like on old gaming system's. I take an old bic pen and pull the ink out. Then I use a lighter to carefully melt the end of the bic pen just enough to be mold-able (Not too much or you could risk melting the plastic housing of whatever you are taking screws out of) and then while it is hot I press the heated end of the plastic down onto the screw making sure it is as straight as possible and holding it there for 2-3 minutes, until it's cooled back to room temperature, with enough pressure that it allows the plastic to mold to the tip of the screw. If done properly you now have a home made screw driver lol.
I figure a bic pen would be too big for the screws on the iphone, but maybe you could find something else, like a cocktail spear or something.
I recommend trying this out on something inexpensive first before trying on the iphone though. I used this tons on like nintendo 64's and gamecube's and stuff and worked great. but sometimes the plastic casing on the system would melt slightly if I heated the pen too much. A little practice though and I haven't done that in a long time. So if you try this you have been forwarned lol. really works good for me though. good luck