Kai Morich's [Serial Bluetooth Terminal] is a good phone app.
(https://play.google.com/store/apps/details?id=de.kai_morich.serial_bluetooth_terminal&hl=en_US&gl=US)
Any program you write to send information to the Serial Monitor can be used to send information to the HC05 BT module.
After your program is loaded to the Arduino, you can connect the HC05 to the hardware serial pins 0/1 and the message from the Arduino will be sent to the monitor and the phone. Serial Input to the Arduino(which you may not require) will only be available from the phone.