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
SprintStart
SprintStart for Sprint Block Performance is the leading tool for your sprint and race start training
$2.99 · In-app purchases
PRICE
$2.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
N/A
No ratings yet
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 included16 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 SprintStart: map the core Health & Fitness 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
Offer a wider variety of sprint training plans and exercises.
Assumption to check: Limited workout options compared to competitors
Validate with people who use this workflow before building.
Hypothesis 2
Implement social features like sharing workouts or challenges.
Assumption to check: No community features for motivation
Validate with people who use this workflow before building.
Hypothesis 3
Include more detailed analytics and visual progress tracking.
Assumption to check: Insufficient progress tracking metrics
Validate with people who use this workflow before building.
Hypothesis 4
Simplify the UI and improve navigation for a better user experience.
Assumption to check: User interface may feel cluttered
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
SprintStart for Sprint Block Performance is the leading tool for your sprint and race start training. Using our sprinting start optimized app, your iPhone and Apple Watch can call the starting sequence and start your race. Record, sync, and share your start training sessions. WIth our reaction time measurement, your response to the starting sound helps you track your performance out of the blocks and off the line. Using your device's acceleration sensors, your reaction time is recorded and displayed, and synchronized via iCloud to all your devices using SprintStart. Trigger a start from the app, from Siri, a shortcut, and your Apple Watch Ultra's Action button. SprintStart - Designed and built by a USATF Level 1 Coach and Masters-level sprint competitor, SprintStart has been track-tested from block, 3-point, and standing starts. You cannot get more convenient, or useful, than SprintStart. See you at the blocks! Features: - Clear voice calling of the starting sequence. - Customized intervals between start commands to model the race environment. - Start from the "bang" or a clear starting tone as your "go" sound. - Uses your device's accelerometer to detect reaction time to the "go" command - and adjustable sensitivity helps ensure you get accurate reaction measurements no matter which device or how you might be carrying or wearing it. - Optionally, display your reaction time at end of each start - your reaction time is always saved. - Export reaction times, dates, and heart rate (available on Apple Watch app) as a CSV to track your training performance over time. - Chart your reaction times for your sprint session right on your device - iPhone or Watch! - Synchronizes start & reaction information via iCloud, accessible on all your devices using SprintStart. - Apple Watch app uses haptic taps along with the voice commands. - Works GREAT with AirPods (especially the Watch app) - eliminate distractions and focus on your training!
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
Redux
Victory Native
React Navigation
React Native Async Storage
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.
