The executable of an app is already encrypted by Apple, and the executable code segment of the app sandbox isn't writeable, so you can't do additional encryption that requires runtime arm code modification. And the optimizer pass of the Objective C/C compiler already creates something very different from the original source code. Using more C and less Objective C will reveal less of your function names, as method names are embedded in visible plain text, but C function names are not. So any trade secret type code should probably be coded in plain C, and compiled with the optimizer turned all the way up. You could obfuscate any webKit Javascript embedded within the app bundle, or any other embedded VM code (as long as interpreted code isn't downloaded).
