One of the benefits of having an iPhone is that you have loads of accessories to choose from. Take for example this contraption from Gary Fong, the once famous photographer, which acts like a tripod.
I like stuff like these but in the end I rarely end up using them as they are not practical. For one, you need to have level ground to shoot from to use it. Now, that's rarely a choice when you are out shooting. A bean bag or a gorrilapod would be a better choice but none of them come with a iPhone rig that enables you to mount it.
There are plenty of tripod mounts for the iPhone but none come with a simple solution.