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How I AIHow I AI

How I built an Apple Watch workout app using Cursor and Xcode (with zero mobile-app experience)

Terry Lin is a product manager and developer who built Cooper’s Corner, an AI-powered fitness tracking app that works across iPhone and Apple Watch.

Claire VohostTerry Linguest
Sep 14, 202536mWatch on YouTube ↗

Summaries, chapters, transcripts, and FAQs on this page are made by uListen, not YouTube.

At a glance

WHAT IT’S REALLY ABOUT

Building Apple Watch workout app via Cursor, Xcode, and structured AI workflow

  1. Terry Lin built “Cooper’s Corner,” an Apple Watch + iPhone workout tracker that lets users speak exercises, weight, and reps, then converts the transcript into structured workout logs with history and analytics.
  2. He started with an ultra-simple MVP: recording Voice Memos on Apple Watch, transcribing with GPT, and dumping results into a spreadsheet—then upgraded to a database-backed system and native apps.
  3. Because iOS development requires Xcode for building/debugging, he “dual-wields” Cursor for coding and Xcode for compilation, simulator/device testing, and watch builds.
  4. He developed a repeatable Cursor process—PRD creation, PRD review (rated for executability), PRD execution, plus refactoring and “rubber duck” learning rules—while managing token/context limits with smaller files and frequent Git commits.

IDEAS WORTH REMEMBERING

5 ideas

Start with a “low-effort” MVP before building the full app.

Terry validated the core behavior by narrating workouts into Apple Watch Voice Memos, then using GPT to transcribe/tag and output to a spreadsheet—proving the value before investing in native apps and backend structure.

Voice-to-structured-data is the real product unlock, not just transcription.

The app doesn’t merely convert speech to text; it extracts exercise, weight, reps, timestamp, and other tags into consistent records that power analytics like top exercises and progression charts.

Mobile AI coding still needs platform-native tooling for build/debug.

Cursor can generate and edit Swift/iOS code, but Xcode remains essential for compilation errors, simulator/device behavior, and Watch-specific builds—so he keeps both tools pointed at the same project folder.

Treat the model like a cross-functional team with a real dev process.

His workflow mirrors org structure: write a PRD, have another “role” review it, iterate until it’s executable, then run a phased checklist with pauses—reducing hallucinations and rework.

Use “PRD review scoring” to predict whether execution will succeed.

By asking a model to rate the PRD (0–10) assuming zero context, he finds missing edge cases, unclear file targets, or inconsistent APIs—then iterates until it’s ~9/10 to enable near one-shot implementation.

WORDS WORTH SAVING

5 quotes

Two months later, I now have an Apple Watch and an iPhone app.

— Terry Lin

They could either work with you or work for you.

— Terry Lin

I realized I was just running into a lot of context windows with these same rules.

— Terry Lin

I call it vibe refactoring.

— Terry Lin

Anything that lets me know what's going on in the mobile.

— Terry Lin

Read the available transcript
Voice-first workout logging (watch/phone)From Voice Memos + spreadsheet to database-backed appCursor + Xcode dual-wield workflowPRD-create / PRD-review / PRD-execute rulesGherkin user stories for requirementsToken/context management via smaller filesVibe refactoring and rubber-duck learning

High quality AI-generated summary created from speaker-labeled transcript.

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