A new feature has been requested to be added to the iOS app binary, that improves the code security. It utilizes the ASLR (address space layout randomization) that Apple has introduced as an important security feature in the latest version of the iPhone's software (4.3+).
The PIE can be enabled when compiling by command line with option -fPIE. Essentially, we need to be able to compile with the command line option -fPIE.
This article explains more about the address space randomization and how iPhone utilizes it: http://money.cnn.com/2011/08/04/technology/iphone_hack/index.htm