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
Cardiogram - HR Monitor
Cardiogram is a private, real-time heart rate monitor, BPM tracker, and workout analysis app designed for iPhone, Apple Watch, and Apple Health users
$3.99 · In-app purchases
PRICE
$3.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 3.5
12 ratings · Top 50%
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.
Build your own version
Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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Combine features and design from your favorite apps.
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What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
What's included18 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
Preview a sample Build Kit No email needed
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 Cardiogram - HR Monitor: 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 Apple Watch support for real-time heart monitoring.
Assumption to check: Limited integration with wearables like Apple Watch
Validate with people who use this workflow before building.
Hypothesis 2
Implement algorithms for better data validation.
Assumption to check: Inconsistent data accuracy
Validate with people who use this workflow before building.
Hypothesis 3
Provide more in-depth analytics and trends.
Assumption to check: Limited historical data analysis
Validate with people who use this workflow before building.
Hypothesis 4
Introduce features for users to share their progress with friends.
Assumption to check: Lack of social sharing features
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
Cardiogram is a private, real-time heart rate monitor, BPM tracker, and workout analysis app designed for iPhone, Apple Watch, and Apple Health users. Monitor, record, and analyze your heart rate during workouts, recovery, daily activity, or rest, with all data stored securely on your device. Unlike subscription fitness apps, Cardiogram works without accounts, cloud services, or data sharing, giving you complete control over your health information. Real-Time Heart Rate & BPM Tracking Track your heart rate and BPM live using Apple Watch or compatible Bluetooth Low Energy (BLE) heart rate monitors. Whether you're training, running, cycling, or monitoring your daily fitness, Cardiogram delivers accurate real-time heart rate data when you need it most. Apple Health Integration & Workout Analysis Import and analyze workouts stored in Apple Health, including sessions recorded with Apple Watch and other compatible fitness apps. Cardiogram automatically keeps your workout history up to date, making it easy to review heart rate trends, training intensity, and performance over time. Recovery Heart Rate Understand how your body recovers after exercise with the 1-minute Recovery Heart Rate metric. Track your recovery across workouts and gain valuable insights into your cardiovascular fitness and training progress. Heart Rate Zones for Smarter Training Visualize workout intensity instantly with color-coded heart rate zones: • Fitness • Fat Burn • Aerobic • Anaerobic • Maximum Effort See how much time you spend in each zone and optimize your workouts for endurance, fat burning, cardiovascular fitness, or peak performance. Privacy-First by Design Your health data stays private. • No account required • No cloud storage • No tracking or data selling • Data stored locally on your iPhone and Apple Health Built for users who want accurate heart rate tracking and workout analysis without compromising their privacy. Wide BLE Monitor Compatibility Connect external heart rate sensors including: • Polar • Garmin • Wahoo • CooSpo • Magene • Other Bluetooth heart rate monitors Ideal for runners, cyclists, gym enthusiasts, and anyone who trains with a Bluetooth heart rate monitor. Fast & Battery Efficient Cardiogram is optimized for long workouts with minimal battery usage, providing reliable heart rate monitoring and workout analysis throughout every training session. Built for Training & Everyday Health Use Cardiogram to: • Monitor your heart rate in real time • Track workout intensity and heart rate zones • Analyze workouts from Apple Health • Measure Recovery Heart Rate • Review heart rate history and trends • Record heart rate sessions • Improve training with actionable heart rate insights Simple, accurate, private, and built to help you better understand your heart rate. Disclaimer: Cardiogram is not a medical device and does not diagnose, treat, or prevent medical conditions. Always consult a healthcare professional regarding health concerns.
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
Supabase
Chart.js
React Navigation
Redux
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.
