Vocalize

Vocalize is a diary I’d dreamed about for years — and one I could only build now. The idea was always the same: a journal you simply talk to, that quietly makes sense of what you said over time. For a long time it stayed a daydream, blocked on two hard problems. LLMs cleared both. They let me prototype and build the app far faster than I ever could have alone, and they finally made the core feature possible — turning rambling, spoken entries into summaries worth reading.

So that’s what it does. Speak freely and it captures your voice notes, transcribes them with Google Cloud Speech-to-Text, and uses Vertex AI to distill the day into a clean summary — then rolls those up into monthly summaries so you can look back across weeks at a glance. You can also open a chat and ask questions across everything you’ve recorded.

I built the first version on Replit and had something working end to end — recording, transcription, and summaries — in under four hours. Once it was real, the catch was cost: Replit hosting added up quickly. So I had Claude Opus rework the code to run on Google Cloud Run instead, which dropped the hosting bill dramatically while keeping the same Express backend, Firebase database, and Vertex AI summarization.