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
Zoiper Premium voip soft phone
Zoiper is an easy to use sip video softphone, with excellent voice quality and easy to setup
$4.99 · In-app purchases
PRICE
$4.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 3.5
132 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/
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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 Zoiper Premium voip soft phone: map the core Productivity 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
Include cloud sync for contacts and call history.
Assumption to check: Limited integration with cloud services
Validate with people who use this workflow before building.
Hypothesis 2
Implement adaptive bitrate management for better call quality.
Assumption to check: Occasional call quality issues
Validate with people who use this workflow before building.
Hypothesis 3
Simplify the UI and improve navigation.
Assumption to check: User interface can be cluttered
Validate with people who use this workflow before building.
Hypothesis 4
Expand international calling options and rates.
Assumption to check: Limited support for international calling
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
Zoiper is an easy to use sip video softphone, with excellent voice quality and easy to setup. Feel free to contact us with support questions or for more information on whitelabel solutions. Connect Zoiper to your PBX or voip provider and make crystal clear, echo free, voice or video calls through wireless and 3g. Zoiper works flawlessly in the background and is optimized to use as little battery as possible while ensuring the reliability of incoming calls. Use bluetooth to pair the Zoiper SIP softphone to your car audio system or your headset and enjoy voip on the go. This softphone comes with a built in QR code scanner for 1 click account configurations. Never type account details and credentials again! Try it for 7 days free! Subscription is not charged if cancelled within trial period. Please note that the in-app subscription purchases are not supported through Family Sharing. 1-Year Subscription: $9.99, 1 month $0.99 USD, automatically renewed until cancelled by the user. Additional Subscription Information: • Subscriptions will be automatically renewed within 24-hours prior to following subscription period. Please check user's Account Setting to disable the auto-renewal. Features: - Call waiting - Call transfer - Call statistics - Call recording - Conference calls - Instant messaging (SIP simple) - Presence (SIP simple) - Encryption (TLS / ZRTP) Supported codecs: - g.711 (ulaw/alaw) - OPUS - G722 - G.722.1 - G.722.1C - Speex - iLBC - gsm - g.729* - vp8 - h264* * The 3rd party patented codecs h264 and g729 are available as optional in app purchase. Zoiper is also available as an OEM / whitelabel solution license and can be customized on demand. Be sure to configure ios to allow notifications for incoming calls for Zoiper and provide access to the contact list. For more information on Zoiper’s features, please visit: https://www.zoiper.com/en/products/zoiperios Terms of use: https://www.zoiper.com/en/zoiper-general-terms Privacy Policy: https://www.zoiper.com/en/zoiper-privacy-policy Regarding the subscriptions: • Payment will be charged to iTunes Account at confirmation of purchase • Subscription automatically renews unless auto-renew is turned off at least 24-hours before the end of the current period • Account will be charged for renewal within 24-hours prior to the end of the current period, and identify the cost of the renewal • Any unused portion of a free trial period, if offered, will be forfeited when the user purchases a subscription to that publication, where applicable
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
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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.
