This is an Android application that turns a smartphone into an SMS/MMS gateway. It exposes a local REST API (Ktor-based HTTP server) for sending and receiving messages, supports cloud server integration via Firebase and Server-Sent Events, and provides webhook delivery, end-to-end encryption (RSA-OAEP + AES-GCM), and device key rotation. The architecture is modular: foreground services (SSE, ping, local server), WorkManager workers for background tasks (message sending, webhook queue processing, inbox upload, settings sync), a Room database for persistence, and Koin for dependency injection. The codebase is well-structured with event-driven communication via a custom EventBus, a validated state machine for message lifecycle, encrypted storage, and rich UI fragments. It supports SMS, MMS, and data SMS, with inbound message capture via broadcast receivers and content observers.