Nice GUI for Arduino /w BT shield
App and Arduino Bluetooth shield are stable combination. Developed a User interface with several screens and up to 40 objects on a screen in past 2 years. Many coding examples available for Arduino IDE library and documentation on the website. Note: alway Arduino or microbit programming needed to get the App to do anything; App is a universal GUI which needs Bluetooth BLE communication and firmware on microcontroller board or shield.