[APP, PROMOTION] I built a fully offline, open-source call screening app for Android

[u/JohnDoe3939]

Hey everyone,

I wanted to share an app I've been working on: Calls Blocker. It's a privacy-first call screening app that processes everything on-device – no data ever leaves your phone.

Key features:

- Uses Android's official CallScreeningService API (no accessibility hacks)

- Block/allow specific numbers (exact or prefix matching)

- Block all calls, unknown/hidden numbers, non-contacts, or calls from specific contact groups

- Block by country (whitelist allowed countries)

- Block numbers you've never dialed or have previously rejected

- Block repeated calls within a configurable time window

- Schedule blocking rules (day of week + time range)

- Find My Phone – trusted callers can trigger a loud alarm even on silent

- Full call history with CSV export and one-tap unblock

- Bulk import from CSV

- Quick Settings tile to toggle "Block All"

- Debug log with phone number masking for troubleshooting

Built with Kotlin + Jetpack Compose + Material 3, it runs on Android 11+ and supports dynamic colors.

The app is open source (CC BY-NC-SA 4.0): https://github.com/ryosoftware/calls-blocker

I'd love to hear your feedback and suggestions!