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
Watch Tuner Lite
Watch Tuner Lite measures the accuracy of mechanical and automatic watches
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 3.2
37 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 included13 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 Watch Tuner Lite: map the core Utilities 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
Enhance microphone filtering for better accuracy.
Assumption to check: Inaccurate tuning feedback in noisy environments.
Validate with people who use this workflow before building.
Hypothesis 2
Offer more features in the free version.
Assumption to check: Limited features without subscription.
Validate with people who use this workflow before building.
Hypothesis 3
Implement a modern and clean UI.
Assumption to check: Poor user interface design.
Validate with people who use this workflow before building.
Hypothesis 4
Add support for various instruments and tuning styles.
Assumption to check: Lack of advanced tuning options for different instruments.
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
Watch Tuner Lite measures the accuracy of mechanical and automatic watches. It uses the built-in microphone or headset microphone to record the audible tick of the watch and calculates the seconds-per-day deviation. Works with almost any 'ticking' watch/clock. Use in a quiet environment. Any ambient noise can affect the accuracy of the results. Complete silence is best. Recommended way to record the ticks is to touch the crown of the watch with the headset microphone. You will get the best results using original Apple EarPods. This is a simple version of Watch Tuner application. Not everyone needs detailed information about a watch movement, sometimes only accuracy is important. Watch Tuner Lite uses very similar algorithm like Watch Tuner does but displays only seconds-per-day deviation. If you want to know how much your watch is fast or slow, this application is for you. If you prefer to measure also beat error and amplitude, try Watch Tuner - a bigger brother of this app. If you need frequency diagram look at Watch Tuner Timegrapher - the most sophisticated app of Watch Tuner series.
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
Zustand
react-navigation
expo-av
react-native-reanimated
BUILD KIT DIFFICULTY
Advanced
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.
