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Lukáš Dobranský
Founder & Developer
When Apple introduced the Foundation Models framework at WWDC 2025, it opened entirely new possibilities for developers. No more paying for every API call to the cloud. No more dealing with latency. And most importantly - user data stays on their device. At Stowly, we fully embraced this technology and the result is fascinating: unlimited story generation for free, right on the iPhone.
Apple Intelligence is a set of AI features integrated directly into the operating system. At its core is the Foundation Models framework - an on-device language model with approximately 3 billion parameters, optimized for Apple Silicon. Unlike cloud-based solutions, this model runs completely on the user's device. That means no API fees, no sending data to servers, and instant response without internet dependency. For developers, it's available through a Swift framework that enables simple model invocation with custom prompts.
Stowly is an app for generating personalized bedtime stories for children. The original plan was to use cloud API. However, we quickly ran into a problem: costs. Generating a single story would cost a few cents. With thousands of users, that would add up fast. And most importantly - how do you explain to parents that they have to pay for every story for their child? When Apple announced Foundation Models, we saw an opportunity. The model is capable enough to generate quality stories adapted to a child's age. And what's crucial - it's free. No API fees, no limits on the number of generations.
Integrating Foundation Models into a SwiftUI app is surprisingly simple. Apple provides the FoundationModels framework with an intuitive API. You create a session, send a prompt, and get a response. The model supports streaming, so text appears gradually as it's generated - creating a pleasant UX effect. The key is proper prompt setup. For Stowly, we created detailed instructions that ensure stories are always age-appropriate, contain educational facts, and new vocabulary words. The on-device model has its limits - it's not as capable as large cloud models, but for our use case, it's more than sufficient.
This is, in my opinion, the most interesting part. Thanks to on-device AI, we were able to create a truly fair freemium model. Users with iPhone 15 Pro and newer can generate an unlimited number of stories completely free. No registration, no credit card. For users with older devices, or those who want premium features - better story quality, AI-generated images, professional narration - we offer Stowly Pro with cloud AI. This model is win-win. Users get value for free, and those who want more can pay for premium features.
In an era when every app collects data, privacy is a strong differentiator. Especially for children's apps. With on-device AI, we can tell parents: your child can request a story about anything, and that data never leaves the device. No server sees it. No company analyzes it. This isn't just marketing - it's technical reality. The model runs locally, prompts aren't sent anywhere, generated stories are saved to the user's iCloud. We have no access to anything.
Apple Intelligence is just the beginning. On-device AI models will become increasingly capable. And what's important - they'll be available on more and more devices. Today Apple Intelligence supports iPhone 15 Pro and newer including the entire iPhone 16 and 17 lineup. For developers, this opens entirely new possibilities. Features that previously required expensive API calls can be free. Personalization that required sending data to servers can be private. Apps that needed internet can work offline. This isn't a revolution that's coming - it's a revolution that's here.
On-device LLM in the form of Apple Foundation Models is changing the economics of mobile apps. For Stowly, it meant the ability to offer unlimited story generation for free, with full respect for privacy. For users, it means value without hidden costs. And for the entire ecosystem, it signals a future where AI isn't a luxury you pay for, but a standard feature available to everyone. If you're developing iOS apps and haven't looked at the Foundation Models framework yet - now is the right time.