There are some iPhone apps already, like AirSharing, which bring some basic file transfer/server functionality to the smartphone. But ServersMan@iPhone, developed by Japanese company FreeBit, promises the full server experience in your hand.
According to ReadWriteWeb, the app lets you read/write to selected directories on your iPhone through a web browser or webDAV protocol. Currently, the ServersMan app is only available in the Japanese iTunes store, but should be available in the US next month. [ReadWriteWeb]