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
Prego OB Wheel
Quick, accurate, easy-to-use obstetrical date calculator and patient tracker designed and developed by family physician Dr
$4.99 · In-app purchases
PRICE
$4.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.9
322 ratings · Top 5%
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 included16 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 Prego OB Wheel: map the core Medical 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
Allow users to input and track additional metrics.
Assumption to check: Limited customization for pregnancy tracking
Validate with people who use this workflow before building.
Hypothesis 2
Offer more features in the free version.
Assumption to check: Requires a purchase for full functionality
Validate with people who use this workflow before building.
Hypothesis 3
Implement a modern UI with updated design trends.
Assumption to check: User interface can feel outdated
Validate with people who use this workflow before building.
Hypothesis 4
Integrate forums or chat for expectant mothers.
Assumption to check: Lack of community 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
Quick, accurate, easy-to-use obstetrical date calculator and patient tracker designed and developed by family physician Dr. Émilie Coudière, MD. Calculate pregnancy dates from LMP, ultrasound, conception, or EDD. Determine gestational age as of any date. Track pregnancies and postpartum patients. QUICKLY CALCULATE • Pregnancy dates from LMP, ultrasound, conception, or EDD. • Patient's gestational age as of today. • Gestational age on future date — i.e. How many weeks will my patient be on June 15th? • Date of future gestational age — i.e. When will my patient be 28 weeks? QUICKLY SAVE • Patients' dates by simply adding a name. • Add quick notes to patients — i.e. Rh, GBS, GTPAL, etc. • Add delivery date to track postpartum patients. QUICKLY REFERENCE • Previously saved patients. • List of upcoming deliveries. • List of postpartum patients. That's it. One screen. Super simple. Enjoy! Enjoying Prego OB Wheel? Please leave a review! It means a lot to us and helps others discover the app. Thanks and take care! * Terms of use are available at https://jeffreyfulton.carrd.co
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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
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BUILD KIT DIFFICULTY
Starter
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.
