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
JB4 Mobile
The brand new JB4 Mobile application is finally ready for public release and has lots of great new features including:
$27.99 · In-app purchases
PRICE
$27.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 3.8
239 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.
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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 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 JB4 Mobile: map the core Sports 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 real-time data syncing features.
Assumption to check: Users report difficulty in data logging accuracy.
Validate with people who use this workflow before building.
Hypothesis 2
Offer more features in the free tier to attract users.
Assumption to check: High price point compared to competitors.
Validate with people who use this workflow before building.
Hypothesis 3
Enhance user support with live chat and FAQs in-app.
Assumption to check: Limited customer support options.
Validate with people who use this workflow before building.
Hypothesis 4
Simplify UI to improve user experience.
Assumption to check: Cluttered interface with too many options.
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
The brand new JB4 Mobile application is finally ready for public release and has lots of great new features including: *Gauge theme customizations *Built-in raw CSV data viewer *Revamped User Adj./WMI data editors *New modern UI completely rewritten from the ground up *More seamless integration with our backend servers JB4 Connect Kit Users: 1) Install the Connect Kit per the installation guide for your vehicle 2) Create your account/sign in with this app 3) Ensure JB4 Mobile has all requested permissions 4) Tap the Connect button in JB4 Mobile About The App: JB4 Mobile is a mobile data logger and display for use with the JB4 tuner from Burger Motorsports. JB4 Mobile allows you to monitor and log multiple parameters from your JB4 equipped car. Parameters such as boost, rpm, fuel trims, air/fuel ratios, ignition advance and much more are available. Current Features: Live gauges Data logging Data graphing Log export via email Code reading/deletion Modify User Adj. (boost, fuel, etc.) settings Modify WMI settings Switch maps on the fly Auto WOT logging JB4 Firmware Updating JB4 ® is a registered trademark of Burger Motorsports Inc ® and is used with written permission.
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
Victory Native
React Navigation
Zustand
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.
