Saylight
A to-do list you talk to: say what you need to do, and the AI voice assistant saves the tasks, sets dates and breaks bigger things into steps — on iOS and Android, in 26 languages.
- Category
- Mobile app / AI voice assistant
- Industry
- Productivity / Consumer
- Website
- www.saylight.app
Saylight is our own mobile product. Instead of typing tasks into a form, you tap the orb and speak naturally — several things at once, with or without dates. The assistant answers live, asks when something is missing, accepts corrections mid-sentence and turns it all into an organised list with goals and steps. The list, goals and reminders are free; the Pro plan adds more minutes of live conversation.
The Challenge
To-do apps fail at the moment of capture: when a thought appears, nobody wants to open a form, pick a date and set a priority. The goal was a list you can fill by simply talking — fast enough to feel like a conversation, reliable enough to trust with your day, and priced so that every paying user is profitable despite the cost of live voice AI.
Our Approach
A native app for iOS and Android built with React Native and Expo, with Firebase as the backend. Live conversation runs over WebRTC; the assistant edits the task list through a defined set of tools. Provider API keys never leave the server — the phone only receives a one-time conversation ticket. Every voice minute is metered server-side against the user's plan, with a per-user cost ceiling and an app-wide kill switch, all adjustable without releasing a new version. Costs were measured on real conversations before pricing was set.
What We Built
- Live voice conversation with the assistant — interruptible, with corrections mid-sentence
- Automatic task parsing: dates, times and priorities from natural speech
- Goals with steps and a map view showing what belongs where and how much is left
- Drag-and-drop rescheduling with undo, morning summary and pre-deadline reminders
- 26 languages — all EU languages plus Ukrainian and Russian — in both the app and the assistant
- Subscriptions (free start + Pro) with a trial, handled server-side via webhooks
- Data stored in the EU; one-tap deletion of conversation history and the whole account
- App Check on every backend function, server-side usage limits and cost ceilings
- Marketing website in 26 languages at saylight.app
Results
- Release builds on iOS and Android passing the same end-to-end scenarios on both platforms
- Automated test suite covering the backend functions, security rules and the app
- Pricing set from measured conversation costs, not estimates
- Live at saylight.app
Tech Stack
React Native with Expo, TypeScript, React Native Firebase (Auth, Firestore, App Check), Firebase Cloud Functions (EU region), ElevenLabs conversational voice over WebRTC, RevenueCat subscriptions, PostHog analytics with opt-out, Next.js for the multilingual website.
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