Feature spec
Goal: Send a clear invoice after finishing a job.
- Add a client, line items, a due date, and payment instructions.
- Preview the total before exporting a PDF.
- Keep an editable draft if export fails.
App Overview
HeartRate++
A simple heart rate complication which gives you an up-to-date overview of your current heart rate on your watch face.
$2.99 · In-app purchases
PRICE
$2.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 2.4
17 ratings · Below Average
Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.
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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included17 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
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Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Screen plan
Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.
States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.
Differentiate and validate
Hypothesis: Contractors need faster repeat invoices more than more templates.
First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.
The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.
Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.
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Free quick prompt For a smaller starting point
Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for HeartRate++: map the core Health & Fitness workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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Opportunities
AI-GENERATED OPPORTUNITY HYPOTHESES
These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.
Hypothesis 1
Add workout tracking and heart rate zones.
Assumption to check: Limited features compared to other heart rate apps
Validate with people who use this workflow before building.
Hypothesis 2
Implement a more modern and intuitive design.
Assumption to check: User interface is not user-friendly
Validate with people who use this workflow before building.
Hypothesis 3
Enhance data collection methods for accuracy.
Assumption to check: Inaccurate heart rate readings in some cases
Validate with people who use this workflow before building.
Hypothesis 4
Integrate with HealthKit and Google Fit for better data sharing.
Assumption to check: Limited support for sharing data with other health apps
Validate with people who use this workflow before building.
App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
App Store description
A simple heart rate complication which gives you an up-to-date overview of your current heart rate on your watch face. The app integrates with the Health app on your iOS device and provides useful information about your heart rate along with a heart rate complication that you can use instead of using the built-in heart rate complication that just displays a Heart Icon without the current heart rate reading, you can use this one to make good use of your watch face space. The app provides a complication for almost every watch, Inforgraph, Infograph Modular, Modular Compact, Modular, and much more. Features: - Heart Rate Complication with an up-to-date heart rate reading. - The app screen gives you real-time reading for your heart rate. - Up-to-date measurement for your current resting heart rate. - 4 hours histogram of your heart rate. - Average, Highest, Lowest Heart Rate for the past 4 hours.
Written user reviews are not shown here. Check current App Store reviews >
Screenshots
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Build scope
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Define the first version
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Set boundaries
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Check the hard parts
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
SUGGESTED BUILD STACK
React Native
Expo
react-navigation
@react-native-community/hooks
react-native-async-storage
expo-chart
BUILD KIT DIFFICULTY
Intermediate
From the Build Kit assessment.
A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.
