Bluetooth app for presence alarm with HC-06 module

To the presence detector with an alarma project, I added an slave (peripheral) bluetooth module (HC-06,) to be mange by an app. It is not BLE so can be manage with earlier (for example an Samsung Galaxy S4 mini and newest mobiles (like a Samsung Galaxy A50.) The next step would be to add a Bluetooth Low Energy module to the project (only available for mobiles with bluetooth v. 5 (like a Samsung Galaxy A50.)

The application, made by means of App Inventor, it is very simple but it works perfectly. It consts of two buttons to connect and disconnect to bluetooth.

And three other for using the presence detector, prove the sound of an alarm 500ms ON and OFF, and an stop button. Each time you select a button, it appears a ✔ symbol to its right so you can know the button selected and thus, the actual state.