Build an Android sync client focused on verifiable one-way backup first, with explicit source and destination rules, transfer checks, retry controls, and failure-only notifications. Support private network storage and self-hosted storage before expanding into two-way synchronization. Provide a readable audit trail showing which files were copied, verified, retried, skipped, or blocked and why.

Users increasingly keep important application data on phones while seeking alternatives to recurring cloud-storage fees and changing provider terms. Recent Android background-execution and service-dependency changes make reliable, independently verified synchronization harder for existing tools.