Then get an iPhone 3GS. There is no such thing as “comparable hardware”. Not even the iOS Simulator is comparable (its OpenGL ES 2 implementation is emulated in software, and provides no hardware support). There are numerous hardware differences that matter, including deferred tile-based rendering which eliminates overdraw (your GeForce card will not perform this) and a unified memory model which eliminates bus transfers to the graphics card.
I want to test my game's performance on roughly comparable hardware, as I develop it.
iOS devices have a virtual memory system but no paging system.
Even threading is not the same.
Both Mac OS X and iOS adopt a more asynchronous approach to the execution of concurrent tasks than is traditionally found in thread-based systems and applications.
The point is that the only hardware that is like an iPhone 3GS is an iPhone 3GS. If you want to develop for one, get one.