Capstone 2 — FitTrack

Tagline: A workout & health-data companion that pulls from HealthKit, syncs via SwiftData + CloudKit, surfaces watchOS complications, and renders rich Swift Charts dashboards.

Tech stack: HealthKit · SwiftData + CloudKit · watchOS complications · Swift Charts · Live Activities · WidgetKit

Time budget: ~2 weeks (3 weeks if you include the watchOS app from scratch)

What this capstone proves:

  • You can ask for HealthKit read & write authorization correctly and survive Apple Review
  • You understand SwiftData + CloudKit sync model, including schema migrations
  • You can ship a watchOS companion with a complication on the Modular and Smart Stack faces
  • You can render production-quality Swift Charts — not the toy bar chart from a tutorial
  • You can implement Live Activities + Dynamic Island for an in-progress workout

The 30-second pitch

“FitTrack is a workout-logging app that pulls heart rate, active energy, and distance directly from HealthKit on iPhone and Apple Watch, persists workouts in SwiftData with CloudKit sync, and visualizes 30-day trends with Swift Charts. The watchOS app runs the workout session with Live Activity updates on the Dynamic Island. The interesting engineering was the HealthKit query observer pattern — I built a single HealthQueryStream that surfaces deltas as AsyncSequence values, which collapses what’s normally 200 lines of HKObserverQuery boilerplate into a clean for try await sample in stream loop.”

Why this capstone

HealthKit is the single most-asked-about iOS framework in fitness-company interviews (Strava, Whoop, Garmin, Apple Health team, Peloton). It has the worst API ergonomics in the Apple ecosystem — building around it well is itself a signal. Combined with SwiftData+CloudKit (the current Apple-recommended path) and a watchOS complication, this capstone covers an unusually wide surface.

Files

  1. requirements.md — feature list, user stories, acceptance criteria
  2. architecture.md — module layout, sync strategy, ADRs
  3. implementation-guide.md — step-by-step build walkthrough
  4. hardening-checklist.md — production + security review
  5. interview-talking-points.md — pitch and Q&A

What “done” looks like

  • iOS app + watchOS app + complication, all on TestFlight
  • HealthKit read/write authorizations limited to the minimum set you actually use
  • 30-day trend chart for at least 3 metrics (heart rate, steps, active energy)
  • SwiftData+CloudKit syncing workouts between two physical devices
  • One Live Activity per active workout, visible on Dynamic Island
  • Hardening checklist fully ticked

Next: Requirements