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
SubStop : Private Sub Tracker
Tired of finance apps asking for your bank login just to track your Netflix bill? SubStop is the 100% private, manual subscription tracker that puts you back in control.
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 5.0
1 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 should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
What's included15 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 SubStop : Private Sub Tracker: map the core Finance 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
Implement proactive reminders and alerts for upcoming payments.
Assumption to check: Users often forget subscription billing dates.
Validate with people who use this workflow before building.
Hypothesis 2
Enhance filtering and sorting options for better organization.
Assumption to check: Difficulty managing multiple subscriptions.
Validate with people who use this workflow before building.
Hypothesis 3
Allow users to create custom categories for subscriptions.
Assumption to check: Limited customization of subscription categories.
Validate with people who use this workflow before building.
Hypothesis 4
Implement strong encryption and privacy policies to protect user data.
Assumption to check: Data privacy concerns regarding subscription information.
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
Tired of finance apps asking for your bank login just to track your Netflix bill? SubStop is the 100% private, manual subscription tracker that puts you back in control. NO BANK LINKING REQUIRED Your data stays on your device. We don't read your emails, we don't connect to your bank, and we don't sell your data. THE 1-TAP CANCEL ROUTER Stop digging through confusing website menus to find the "Cancel" button. SubStop's Smart Router detects where your subscription is from and instantly takes you directly to the exact cancellation page. PAY ONCE. NO SUBSCRIPTIONS. You shouldn't have to pay a subscription to track your subscriptions. Pay once, own it forever. SMART OFFLINE ALARMS SubStop automatically calculates your billing cycles and sets secure, offline alarms on your device. Get notified 5 days and 24 hours before a charge hits so you never miss a cancellation window again.
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
React Navigation
Zustand
React Native Paper
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.
