On the app's page, I'd suggest clearly describing what one gets for free (before paying for a plan), so people can try it. For an app like this, I'd want to know what I'm getting before I install. Many apps just install and ask you for a credit card before anything happens. From there, I'd like to know what I'm paying for before I swipe my credit card. Clearly describing free versus paid version is key.
But my last iOS device is an iPad 2, so I don't think I can even do the free version.