A bit like the integration with commerce whereby members can use credits against items in downloads app, maybe as others suggested, allow to set events, like new registrations, login, daily reward etc, the admin can create the events and set the x amount of credits a member receives, like the credits system used in xenforo, it integrates with resources (downloads plugin) and allows, from a set list, events to be created.
I can provide screens from the xf system if it helps explain better.