So, it turns out that I’m probably not going to use the Hijack approach to getting serial data from my Mindflex into my iPhone.  This is mainly due to the fact that I have the majority of the components to build a similar system from scratch.  The difference will be that I will not use the iPhone’s battery to power the system; I will use an external power source.  I intend to follow the steps detailed in this forum discussion that I found on Arduino’s website: Arduino–>FSK—>Iphone (OpenframeWorks)

Here is a snapshot and the corresponding schematic of the setup of the parts:

Setup: Arduino > iPhone Audio Jack
Schematic

NOTE:  If you don’t mind jailbreaking your iPhone, the setup documented here interfaces the iPhone through the 30-pin dock at the bottom of the phone.  It allows for a faster baud rate and easier access to the iPhone’s power source. Apparently you have to buy the Redpark or Legacy (?) device for ~$60, however.