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
Saily: eSIM Data for Travel
Tired of shocking roaming bills and spotty airport Wi-Fi? Saily brings fast mobile data to your iPhone in 200+ destinations
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.7
12,585 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.
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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 included17 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 Saily: eSIM Data for Travel: map the core Travel 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
Provide a wider variety of data plans and customizable options.
Assumption to check: Limited data plan options can lead to user frustration.
Validate with people who use this workflow before building.
Hypothesis 2
Implement a more guided onboarding process to familiarize users with the app.
Assumption to check: In-app navigation can be confusing for first-time users.
Validate with people who use this workflow before building.
Hypothesis 3
Introduce a live chat feature for immediate assistance.
Assumption to check: Customer support response times may be slow.
Validate with people who use this workflow before building.
Hypothesis 4
Add a review and rating system for users to share their experiences.
Assumption to check: Lack of user reviews for data plans makes decision-making difficult.
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 shocking roaming bills and spotty airport Wi-Fi? Saily brings fast mobile data to your iPhone in 200+ destinations. Get a prepaid eSIM before you fly and connect to local networks the moment you land. What is an eSIM? An eSIM is a virtual SIM for your iPhone. There’s no tiny plastic card to swap — just install the eSIM profile once, and you’re ready to connect wherever your trip takes you. Why Saily? No roaming fees: Get affordable prepaid mobile data instead of surprise carrier charges. 200+ destinations: Mobile data from the top local networks around the world. Instant setup: Install your eSIM in minutes, right from your phone. Keep your number: Your primary line stays active for calls and texts. Flexible plans: Pick from local or multi-destination data plans. Top up anytime: Add more mobile data in a few taps, wherever you are. Track your usage: Keep an eye on your eSIM data usage, all in one app. Built-in security features: Browse more safely with the Ad blocker and Web protection. NordVPN pedigree: Built by a team with years of digital security experience. Perfect for every traveler Business trips: Join meetings and send emails with reliable cellular data. Digital nomads: Run a mobile hotspot and work from 200+ destinations with fast data speeds. Vacationers: Post photos and navigate new streets without worrying about connectivity. Group travelers: Share your data with up to 4 travel buddies using shared plans. How it works Install the app: Download the Saily eSIM app and pick your destination. Pick a plan: Select a prepaid mobile data plan for your trip. Set up your eSIM: Follow the on-screen steps to install the eSIM profile. Get online: Your data plan will start the moment you land. What can you do with Saily? Stream shows, map your route, or work remotely — all on mobile data, without buying a local SIM card or relying on public Wi-Fi. Optional US phone number Get a dedicated US second number (+1) directly in the Saily app for just US$0.99/month, and add flexible call and text plans whenever you need them. Stay connected at sea Sailing on a cruise? Regular data won’t work in open waters — grab a Saily cruise plan to stay online aboard select cruise lines. No hidden fees or contracts Pay only for the prepaid eSIM data you need, or upgrade to a flexible Saily Ultra subscription. No long-term contracts or unexpected roaming charges on your next bill. Compatibility and support Most recent iPhone models support eSIM technology. If you run into questions about setup, coverage, or your data plan, the Saily support team is ready to help 24/7. Travel data made simple Pick a mobile data plan that fits your trip and connect the moment you arrive, with transparent pricing and no roaming surprises!
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
Zustand
React Navigation
React Native Reanimated
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.
