Auto-Reply Android App Development

I'm seeking a ready-made Android application that can automatically send SMS or WhatsApp messages when a call is missed or received.

The app should ideally include the following features (or be customizable to add them later):
- Auto-reply via SMS and/or WhatsApp
- Message triggers for missed or attended calls
- Option to enable/disable auto-reply
- Customizable auto-reply messages
- Option to customize auto-reply messages for different contacts
- Call log with auto-replied records
- Firebase or backend integration for remote message updates (optional)
- Clean UI with Material Design

If you already have such an app or something similar, please share:
- Demo APK or screenshots
- List of features
- Technology stack used
- Pricing (with source code)

I'm open to customization if the core functionality matches. Looking forward to your proposals!