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
TrainsFYI: Train Map & Tracker
Track passenger trains across the globe, and see where your train is right now.
Free
PRICE
Free
No in-app purchases
BUSINESS MODEL
Free
No overall Grossing estimate available
RATING
★ 4.6
60 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
Make this idea yours
A product spec, screen plans, and build steps for your coding agent.
First kit free with a verified email
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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 included
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 TrainsFYI: Train Map & Tracker: map the core Navigation 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 offline maps with download options.
Assumption to check: Limited offline functionality for map access.
Validate with people who use this workflow before building.
Hypothesis 2
Enhance tracking with more frequent updates and alerts.
Assumption to check: Inconsistent real-time tracking updates.
Validate with people who use this workflow before building.
Hypothesis 3
Allow users to set preferences for notification types.
Assumption to check: Lack of customizable notifications.
Validate with people who use this workflow before building.
Hypothesis 4
Integrate with buses and rideshares for comprehensive transport solutions.
Assumption to check: Limited integration with other transport services.
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
Track passenger trains across the globe, and see where your train is right now. TrainsFYI is your real-time map and tracker for passenger rail. Whether you are a transit fan, traveler, or just curious, you can explore active trains and follow their journeys. Whether you are checking your Amtrak route, following the New York MTA Subway, tracking BART across the Bay Area, or just exploring rail activity worldwide, TrainsFYI makes it fun and easy to see where the trains are right now. FEATURES: • Interactive Map — Watch train positions update live across the world. • Follow Individual Trains — See routes, stops, and estimated arrival times. • Browse by Network — Explore 140+ supported transit agencies. • Zoom Anywhere — From your local station to cross-country journeys. SUPPORTED US NETWORKS: Amtrak, MTA New York City Subway, BART, Caltrain, Metra, Chicago Transit Authority, NJ Transit, Long Island Railroad, Metro-North Railroad, Massachusetts Bay Transportation Authority, Washington Metropolitan Area Transit Authority, Metrolink, LA Metro, Sound Transit, TriMet, SEPTA, SunRail, Brightline, RTD Light Rail, Valley Metro Rail, San Diego MTS, Pittsburgh Regional Transit, Tri-Rail, ACE, MetroLink, ION Light Rail, South Shore Line, Metro Transit, KCATA, EMBARK, VTA Light Rail, San Francisco Muni, Virginia Railway Express, MARC, Dallas Area Rapid Transit, MARTA, Maryland Metro, and more. SUPPORTED CANADIAN NETWORKS: VIA Rail, GO Transit, Toronto Transit Commission, TransLink SkyTrain, STM (Société de transport de Montréal), Réseau Express Métropolitain, Exo, OC Transpo, UP Express, Edmonton Transit Service, Calgary Transit CTrain, and more. MORE NETWORKS WORLDWIDE: ScotRail, LNER, Elizabeth line, London Overground, Great Western Railway, Eurostar, SNCF, DB Fernverkehr, S-Bahn Berlin, S-Bahn München, SL, SJ, Renfe, Sydney Trains, Sydney Metro, Yarra Trams, Auckland Transport, Indian Railways, and more. COUNTRIES COVERED: United States, Canada, United Kingdom, Germany, Sweden, France, Spain, Argentina, India, Australia, New Zealand, Malaysia, Mexico, Egypt, Finland, Belgium, Netherlands, and more. COMING SOON: We are expanding coverage to more countries and networks, including major rail systems in Europe and Asia. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
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-native-community/geolocation
react-native-maps
zustand
BUILD KIT DIFFICULTY
Not assessed in a Build Kit yet.
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.
