TapReply

TapReply: double-tap the Apple logo on the back of your iPhone and get the right reply. Next Gen Award entry.
Test tab: double-tap the back of your iPhone on a sample chat, TapReply writes the reply and copies it for you.
Studio: pick a tone (Professional, Charmer, Funny, Fact Check) or create your own.
TapReply app icon (1024 x 1024).

🎓 Entry: Next Gen Award (student)

I'm Pierre, a student at Audencia (France), and I designed and built TapReply on my own. TapReply is live on TestFlight (App Store review in progress), so this is a Next Gen Award entry with a public open-source repository and a demo video.

Inspiration

The Apple logo on the back of your iPhone is actually a button: tap it twice and iOS can run any action (Settings > Accessibility > Touch > Back Tap). Meanwhile, we all do the same tedious dance every day: screenshot a chat, open an AI app, paste it, ask for a reply, copy the answer, go back, paste. I wanted that hidden button to do all of it in one gesture.

What it does

TapReply writes your replies for you, from any conversation.

Double-tap the back of your iPhone, in any chat.
TapReply reads the conversation on your screen and writes the right reply.
The reply is copied and shown in the Dynamic Island. You paste it and send it.

Messy draft? Type "cant tmrw.. busy?? fri maybe", tap twice, and it becomes a clear, natural message that keeps your meaning.
Tones: Classic, Professional (work emails), Charmer (dating apps), Funny (group chats), and Fact Check, which reads a claim on your screen and tells you if it's TRUE or FALSE.
Create your own tones in the Studio: name, mascot color and instructions.
Three shortcuts: Double Tap, Triple Tap and the Action Button, each with its own tone.
Private history saved on the iPhone only, with favorites.
A built-in Test tab to try the gesture safely. Available in 6 languages.

Privacy

Screenshots never leave the iPhone: text is read on the device with Apple's Vision framework.
Only the conversation text is sent, and only after explicit consent (you can turn it off anytime).
Zero-data-retention AI providers only: the text is processed in real time and never stored.
No account, no ads, no tracking.

How RevenueCat powers the business

Free: 10 replies granted once by the server as RevenueCat Virtual Currency (RPLY), plus 1 custom tone.
TapReply Pro (monthly or annual, 3-day free trial on annual): unlimited replies for personal use, extra tone shortcuts, unlimited custom tones, exclusive app icons.
50-reply pack: a one-time purchase for people who don't want a subscription.
Credits can't be faked on the device: the server checks the entitlement and the balance with the RevenueCat REST API v2, debits one credit before calling the AI and refunds it automatically if the generation fails.
When Pro ends, extra tones and Pro shortcuts lock gracefully with a clear explanation instead of disappearing.

How I built it

iOS app: SwiftUI (iOS 18+), App Intents + a shared Shortcut triggered by Back Tap, Vision OCR with a custom parser (who said what, and the draft in the input field), ActivityKit Live Activities for the Dynamic Island, SwiftData, String Catalogs for 6 languages.
TapTap, the mascot: a real-time vector animation engine I built for the app: 50+ animation clips in a compact custom format, decoded at runtime and recolored with the user's color.
Backend: a Supabase Edge Function in TypeScript that verifies the anonymous RevenueCat identity, applies rate limits, manages credits through RevenueCat, and calls AI models through OpenRouter (Gemini, with Claude as fallback).
Monetization: RevenueCat SDK, offerings, entitlements, virtual currency and REST API v2.

Challenges I ran into

Reading a screenshot reliably: telling my messages from the other person's, ignoring timestamps and app chrome, and finding the draft in the input field.
Making credits impossible to cheat without any user account, using only the anonymous RevenueCat ID and server-side debits.
Getting privacy right: explicit consent, zero data retention, and App Store review rules for AI apps.
Explaining a gesture most people have never used: that's why the onboarding is an animated, step-by-step story with TapTap.

Accomplishments that I'm proud of

A complete product built solo as a student: onboarding, tones, custom tones, history, paywall, subscriptions, credits, privacy, 6 languages, now in App Store review.
Replying to a message takes two taps instead of seven steps.
Proof that students don't just learn to build apps: we ship them.

What I learned

Shipping is a different job from coding: review rules, privacy labels, pricing, trial terms, onboarding, and above all explaining a new habit in a few seconds.