Shipping an Android podcast player with on-device Whisper — 6 lessons from a Czech indie launch

After a year of nights and weekends, I shipped Lucidcast — an Android podcast player I built because every mainstream app I tried was missing the same three things. The app went live on Google Play this week. This post is for indie devs thinking about shipping their own Android project — six lessons I learned the expensive way. What Lucidcast does (90-second context) A podcast player with on-device AI: Whisper transcribes downloaded episodes locally (audio never leaves the phone) AI episode summaries via Gemini, with a live progress ring "Podcast" wake-word voice commands that work on the lock screen and in Android Auto Smart Pause auto-pauses on loud noises or when someone talks to you Plus the usual: chapters, transcripts, value tags (Podcasting 2.0), 22 languages, Android Auto, live radio, no accounts, no ads. Free includes the full podcast player. Pro one-time unlocks the audio intelligence engine. AI Pack subscription enables Whisper + summaries. Made in EU by a one-person Czech indie team (Prismatic s.r.o.). Play Store | Landing OK, lessons. 1. On-device Whisper is harder than it looks (NDK 29 patch needed) I wanted local transcription so audio doesn't leave the device. whisper_ggml is the only Flutter binding I found that works end-to-end. Catch: it needs Android NDK 29.0.13113456 while most other plugins are still on 27. Setting ndkVersion = "29..." in android/app/build.gradle.kts works for new builds, but the plugin's auto-detected version was sometimes off — needed a small patch script ( flutter/tool/patch_whisper_ggml.sh ) to enforce it during CI. Battery cost is real: I gate transcription to charging-only mode by default with a configurable battery threshold (10-80 %, default 50 %). When the user toggles "transcribe downloaded episodes," I queue the work but only execute when the phone is plugged in. Users on r/podcasts would otherwise notice a 5-10 % overnight battery drain. 2. Sharing the microphone is a contract nobody documents Smart Pause uses noise