Adding subscriptions to a native app means learning StoreKit and Play Billing. Two platforms, two languages, two sets of documentation. Then you try to wire it all up to your Rails backend.
PurchaseKit gives you drop-in bridge components for iOS and Android. Your paywall stays in ERB. No Swift, no Kotlin.
It also normalizes Apple and Google webhooks into four events (created, updated, canceled, expired) so you don't have to deal with their different formats.
Works with the Pay gem or your own models.
Free for up to 10 paying customers, $99/mo after.