First Bank of Pig

A simple, open source, Android piggy bank app for tracking kids' savings. Parents manage transactions and family membership, and kids can view their transactions and balance. No ads, and no logins for children.

Features

• Parent Mode: Create family, add children, manage transactions (deposits/withdrawals), invite other parents
• Kid Mode: View balance and transaction history (read-only)
• Device Security: Kid devices register by scanning parent's QR code (no login required!); parents can manage kid devices and revoke access at any time
• Biometric Lock: Parent mode is protected by fingerprint/face/PIN
• Real-time Sync: Instant updates across devices
• Theme Support: System, light, and dark mode

Install from the Play Store

You don't need to build it yourself. It's free on the Play Store!

I do pay a small amount in cloud computing costs to run the app. Donations are welcome through GitHub Sponsors.

Setup and Build

See docs/SETUP.md for complete setup and build instructions.

Architecture

• Kotlin with Jetpack Compose for UI
• Firebase Authentication (Google Sign-In for parents, Anonymous for kids)
• Firebase Firestore for data storage
• Material 3 design system

Data Model

/families/{familyId}/
  name, ownerUid, createdAt
  parents/{uid}: { email, joinedAt, inviteCode? }
  invites/{code}: { code, expiresAt, createdBy, familyId }
  children/{childId}: { name, createdAt }
    devices/{deviceUid}: { deviceName, registeredAt, lastAccessedAt }
    transactions/{txId}: { amount, description, date, createdAt, modifiedAt }

/inviteCodes/{code}: { familyId, expiresAt }
/childLookup/{code}: { familyId, childId }

Balance is computed client-side by summing transactions.

License

MIT