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
RaceChrono Pro
RaceChrono Pro is a versatile lap timer, data logging and data analysis app designed especially for use in motorsports, replacing your traditional lap timers and data loggers
$19.99 · In-app purchases
PRICE
$19.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.7
181 ratings · Top 15%
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 RaceChrono Pro: 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
Add more detailed analytics and comparison tools.
Assumption to check: Limited analysis features compared to competitors
Validate with people who use this workflow before building.
Hypothesis 2
Offer a more affordable subscription model.
Assumption to check: Higher price point may deter users
Validate with people who use this workflow before building.
Hypothesis 3
Implement a guided onboarding process.
Assumption to check: Complex setup process for new users
Validate with people who use this workflow before building.
Hypothesis 4
Include social sharing and community challenges.
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
RaceChrono Pro is a versatile lap timer, data logging and data analysis app designed especially for use in motorsports, replacing your traditional lap timers and data loggers. The RaceChrono Pro app also enables you to record videos and overlay them with the logged data. RaceChrono apps have a strong following, currently over 100000 active users. If you look around at pits during your race or track day, chances are that you’ll see someone using RaceChrono. Even many professionals, such as factory test drivers and race driving instructors, are known to use this app! No matter whether you ride motorbikes, drive go-karts or cars, on closed circuit or special stage tracks – this is the motorsports app for you. RaceChrono Pro has following major features: • Lap timing with sectors and optimal lap • Track library of over 2600 pre-made race tracks • Custom user defined circuit and point-to-point tracks • Smoothly scrolling data analysis with synchronised graph, X/Y graph, map, video and comparison video • Predictive lap timing and time delta graph • Hardware accelerated video export with configurable data overlay • Multiple camera recording and picture-in-picture video export • Video recording using internal camera • Linking and synchronising video files from almost all action cameras • Support for external GPS receivers; Dragy Pro/DRG70/DRG70-C/Lite, RaceBox Mini/Mini S/Micro, Qstarz BL-818GT/BL-1000GT/LT-8000GT, Columbus P-9 Race, Dual XGPS 150/160, VBOX Sport, Garmin GLO • Support for OBD-II readers; OBDLink MX+ Bluetooth, OBDLink CX Bluetooth, Dragy OBD, Vgate vLinker FS, Vgate vLinker/iCar BLE, PLX Kiwi 3/4, Carista OBD2 Bluetooth, Tonwon BLE 1/2/Pro, Veepeak OBDCheck BLE, UniCarScan UCSI-2000, OBDLink MX Wi-Fi, generic Wi-Fi OBD-II • Support for Bluetooth LE heart rate monitors • Unlimited session length, good for 24 hour races • Session data export in .ODS (session summary for Excel), .NMEA, .VBO and .CSV formats
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
axios
react-navigation
expo-graph
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.
