Cross-Platform Utility App Development

I need a straightforward utility app built from the ground up for both iOS and Android. The single must-have feature is seamless data synchronization, so users can start a task on one device and pick it up instantly on another without friction... (Budget: ₹400 - ₹750 INR, Jobs: Android, Flutter, iOS Development, iPhone, Kotlin, Mobile App Development, React Native, User Interface / IA)