Mentalium — CBT Diary by Voice

Early-stage but live: the app is published on the App Store across 7 markets (EN, ES, FR, PT-BR, DE, IT, RU) and the promo site at mentalium.me is indexed in Google, Yandex and Bing in all 7 languages. Current monthly reach is organic and growing, driven by SEO, a multi-language Pinterest presence, a YouTube demo, and technical articles on Dev.to, Hashnode, Medium and HackerNoon. Addressable audience is large: CBT is the most widely practised evidence-based talk therapy, and structured thought-record homework is a near-universal part of it — anyone in or starting CBT is a potential user.

Three groups. (1) People actively in CBT with a therapist who want their thought-record homework to actually get done — captured in the moment instead of reconstructed from memory before a session. (2) Self-guided CBT practitioners managing anxiety, depression, stress, OCD or panic. (3) People with ADHD, for whom speaking removes the "I can't sit down and write it out" barrier that makes traditional journaling fail. Consumer self-help product (B2C), not enterprise — no notable corporate customers; value is direct to the individual and, indirectly, to their therapist via an exportable session report.

Other, Flutter / Dart, Riverpod, SQLite (sqflite), Whisper.cpp (ggml-small-q5_1, ~181 MB) running fully on-device — iOS via Metal GPU, Android via JNI — for offline speech-to-text, fl_chart for progress graphs, PHP + MySQL backend used only as an encrypted email relay (AES-256-GCM), RevenueCat for subscriptions, AppMetrica for analytics. No cloud AI and no server-side voice processing — all transcription happens locally on the device.

Deployed and live (not pre-launch): • App Store: https://apps.apple.com/app/id6764609587 • Promo site, 7 languages, indexed: https://mentalium.me • Demo video: https://youtube.com/shorts/EV2HcHoCHHY • Technical write-ups: Dev.to (https://dev.to/pavel_trubetskov/i-built-a-voice-cbt-diary-with-offline-ai-heres-how-it-works-23c6), Hashnode (https://trubetskov.hashnode.dev/on-device-ai-for-a-mental-health-app-what-i-learned-building-mentalium), Medium (https://medium.com/@p.trubetskov/on-device-ai-for-a-mental-health-app-what-i-learned-building-mentalium-17e036e4ec6a) • Press: PRLog (https://www.prlog.org/13148471-mentalium-launches-voice-cbt-diary-with-offline-ai-transcription-on-the-app-store.html), OpenPR (https://www.openpr.com/news/4529189.html), 1888PressRelease (https://www.1888pressrelease.com/mentalium-launches-voice-cbt-diary-with-offline-ai-transcrip-pr-767133.html) • Listings: LinkedIn, Crunchbase, Wellfound, F6S, Trustpilot, Behance Android version is in active development. As a recently launched indie product, growth so far is organic; the projection is steady SEO/content-driven acquisition across all 7 markets.