Yes, you can use IAP to sell a subscription based iOS app. I have an iOS app and a Mac Store app that use this approach.
There are two types of IAP subscriptions available - auto-renewable subscriptions and non-renewable subscriptions.
My understanding is that for non-content based apps, you need to use the non-renewable subscription.
So that’s what I do. I sell a 12-month “premium subscription” as an IAP in my app.
That allows me to have my app on the App Store for free (which nets it many more downloads than it would as a paid app). A small percentage of the users purchase the subscription. It’s been less than 12 months, so I don’t know how well people will buy the next subscription when theirs expires.
There’s other benifits to this approach. When people sign up for the subscription, it’s a chance to capture their email address (must be an optional field though). Finally I can get some info on who my customers are
Anyway, depending on what your subscription unlocks will depend on whether it will be approved or not. My subscription removes advertisements, backs up the users content to the “cloud” (my server where I can do some analytics on how they’re using the app), enables printing, gives them “premium support”.
So it’s not a bad way to go. Probably better than having separate “lite” and paid versions of your app.