Inspiration
Traditional spam call blocking apps often require invasive permissions, uploading the user's entire address book to commercial reverse-lookup directories. We built Callro to prove that smartphone users—especially seniors and families targeted by aggressive phone scams—can get carrier-grade call screening directly on their device without surrendering their privacy.
What it does
Callro is an on-device spam call blocker for Android:
• Native Screening: Uses Android's ROLE_CALL_SCREENING API to screen incoming calls in real time before the phone rings.
• On-Device Cryptographic Checks: Inspects STIR/SHAKEN carrier certificates and dynamic neighbor spoofing signatures locally.
• Scoped Privacy: Contacts, call logs, and audio never leave the device.
• Fortress Mode: A senior-friendly toggle that restricts incoming rings strictly to saved contacts.
How we built it
Callro is developed with Flutter and Dart, with native Android Kotlin services interfacing directly with the Android Telecom subsystem. Subscriptions are $9.99/month with a 7-day free trial and no card required.
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