XiL PRO is a free Android application developed by Steven Liu under the Utilities & Tools category. It allows users to remotely control four-axis aircraft using their mobile phones. The app uses 2.4G WiFi protocol to transmit real-time video taken by the aircraft's camera to the mobile phone.

With XiL PRO, users can also take photos and record videos directly on their mobile phones. The app supports 720P and VR, providing a high-quality viewing experience. The app's user interface is simple and easy to navigate, making it accessible for both novice and experienced users. Overall, XiL PRO is a great choice for those looking for a convenient way to control their four-axis aircraft from their mobile device.