The problem is that your list is so big (both long and we were working with a lot of columns and a few equations) that Excel on my computer couldn’t handle it. I have a ton of memory on my computer, but it wasn’t sufficient. For example, when I tried a simple task like sorting the list, it would take several minutes to process the operation. I would literally click ‘Sort’ and then go and work on another task for a while.
I am not signing up for an account so I don't know exactly how the API works, but if I were setting up an iPhone App to work with this, I would use the rails plugin. Rails gives you JSON communication for free (IE no extra work required) see section 2.2.9. Then use on IOS app use something like: to interact with that.

After you have entered your "List Name" you will need to enter a "List Description." Here is where you will describe the kind of information you'll be sending from this list. There is a 400 character limit for the "List Description." Subscribers will see your "List Description" on the unsubscribe page if they ever go to unsubscribe from your list. Once you are done entering your "List Description" click the "Next Step" button.