Sure. No Problem. Can you tell me what type of server this native iphone application connects to and then I can tell you how to performance test the server? What server your application connects to will in large part determine how you collect the conversation between the client and the server, what tools you can use to reproduce the load enmasse and what your level of effort is likely to be.
Your server generally has no clue as to what platform the client is running on unless the client tells the server in the handshake that it is running on blah-blah-blah OS with yada-yada-yada client version. As an example you can look to two sources of information, one is the server logs for a web server which will tell you quite a bit about the connecting client, the second being a sockets level trace of an ORACLE client handshake to a server which will also announce quite a bit about the client type.