Squirl - Voice Journal

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What it does

Screen-Free Voice Capture: Tap an NFC sticker on your pill bottle, tap the Action Button, or tell Siri "Record check-in." Speak for 30 seconds while walking down the hall, and walk away.
100% On-Device Signal Extraction: Transcribes locally and extracts mood, focus, energy, and medication side effects into a visual timeline.
Zero Shame: No streaks, no red badges. If you miss two weeks, Squirl simply says: "Welcome back."
Absolute Privacy: No accounts, no servers, and zero cloud leaks ($\text{Marginal Cloud Inference COGS} = \$0.00$). Your journal never leaves your iPhone. ## How we built it
WhisperKit (CoreML): Runs openai_whisper-small directly on the Apple Neural Engine.
On-Device LLM (Apple MLX): Runs Qwen2.5-1.5B-Instruct-4bit locally in a two-pass pipeline (narrative summary + structured JSON extraction against a 718-entry ADHD clinical lexicon).
RevenueCat: Powers our $29.99/year subscription and 7-day free trial.
Fail-Open Architecture: If offline or if entitlement check fails, the app automatically unlocks. Your private journal is never held hostage. ## Challenges we ran into
Local RAM & Thermals: Running Whisper + a 1.5B LLM on-device risks memory pressure ($>1\text{ GB}$). Solved with a 1.5s staggered preload, a $20\text{ MB}$ MLX cache limit, and 3-minute idle memory eviction.
Interrupted Model Downloads: Large weight downloads often broke on mobile data. Built an out-of-process BackgroundLLMDownloadService with byte-range resume so interrupted downloads never start from zero.
Ethical Paywall Design: Avoided dark patterns, fake countdowns, and streak threats. Existing 1.0 users are grandfathered, and journal export remains free forever. ## Accomplishments that we're proud of
Shipped Solo: Built, tuned, and published code-complete to the App Store with $\$0$ outside capital.
$\mathbf{\$0.00}$ Server Bills: 100% on-device AI gives us $85\%$ net margin realization on every subscriber.
Proven Accuracy: On-device benchmark gate scored $0.941$ precision/recall on ADHD medication extraction. ## What we learned
Lower activation energy > more features: A 30-second voice note beats a 10-minute form every single time.
Calm technology wins: ADHD users don't need gamified streaks; they need permission to pause and psychological safety when they return.
Edge AI is production-ready: Local inference delivers instant privacy, zero latency, and zero server scaling headaches. ## What's next for Squirl - Voice Journal
Squirl Connect: Opt-in clinical summaries to export structured titration and symptom reports directly to your psychiatrist.
Apple Watch & Lock Screen Widgets: One-tap complication logging.
Encrypted CloudKit Sync: Optional private end-to-end sync across iPhone and Mac without compromising the on-device privacy guarantee.