SendTo ScreenMate for iOS

Send what's on your iPhone (a YouTube video, a web page, a Maps place or an address) to an Android screen in your car running ScreenMate Receiver.

• Share sheet: Share → SendTo ScreenMate sends immediately and closes.
• Shortcuts action: "Send to ScreenMate" runs in the background, so it works from an NFC tag, Back Tap, the Action button or Siri.
• End-to-end encrypted: AES-256-GCM with a key that only your phone and your screen know.
• No account, no backend of our own: messages travel through ntfy (public or self-hosted), and the server only ever sees ciphertext.

Build and install

Requires Xcode 16 or later and an iPhone on iOS 18 or later. A free Apple ID works for personal installs.

1. Copy Config/Local.example.xcconfig to Config/Local.xcconfig and set:

   • BUNDLE_PREFIX: a reverse-DNS prefix you control, e.g. com.yourname
   • DEVELOPMENT_TEAM: your Team ID (Xcode → Settings → Accounts)

   Local.xcconfig is git-ignored, so your personal values never end up in the repo. Avoid picking a team in Xcode's Signing & Capabilities tab; that writes your Team ID into the project file.

2. Open SendToScreenMate.xcodeproj, select the SendToScreenMate scheme and your iPhone, and press ⌘R.

3. On the car screen, open ScreenMate Receiver. In the iPhone app, tap Scan QR code (or pick a photo of the code, or paste the pairing text).

Shortcuts and NFC

Example automation (Shortcuts → Automation → + → NFC):

1. Get On-Screen URLs
2. Get On-Screen Postal Addresses
3. Text containing both results
4. Send to ScreenMate with Content = Text

Optionally add Take Screenshot and pass it as the action's Screenshot: when the on-screen content has no link or place, the screenshot is read on-device for one.

Apps that don't expose their content to Shortcuts (YouTube, for example) work through the share sheet instead.

Siri

Say "Show this on ScreenMate" (or "Cast this to Car Screen") while a page is open. Phrases starting with "Send" are avoided because Siri treats them as messages to a contact. With Apple Intelligence, Siri may pass the on-screen page straight to the action's Web Page input, which carries the full address. Shortcuts that read the screen themselves only see the domain Safari displays, so for Safari pages use this phrase or the share sheet.

Wire protocol

Item	Format
Pairing code	`server
Payload	JSON {"url": "...", "title": "..."}
Encrypted body	Base64(12-byte nonce ‖ AES-256-GCM ciphertext ‖ 16-byte tag)
Publish	POST <server>/<topic>
Receipt	the Receiver publishes the message id to <server>/<topic>_ack

Apple Maps links and plain addresses are converted to geo:0,0?q=… so Android navigation apps understand them.

Project layout

App/             SwiftUI app, QR pairing, Shortcuts action
ShareExtension/  share sheet extension
Shared/          protocol, encryption, link parsing, publisher, pairing storage (used by all targets)
Tests/           unit tests (run in CI on every push)
Config/          xcconfig, Info.plists, entitlements
Scripts/         project generator

Source folders are synchronized with the Xcode project, so adding a Swift file needs no project change. If targets or build settings change, regenerate the project with python3 Scripts/generate_project.py.

License

MIT. See LICENSE.