I recommend using Flutter for your cross-platform mobile app development, especially since you already have experience with iOS and Android programming. Flutter offers a seamless way to create a single codebase that works on both platforms. Its expressive UI, hot-reload feature, and extensive widget library make it an excellent choice for developing a control device for robots over Wi-Fi. Flutter’s Dart programming language is beginner-friendly, and the framework itself provides comprehensive documentation and an active community for support. This will streamline your development process and allow you to focus on creating a robust and efficient application for both iOS and Android platforms.