Hardware advice please

Projects General Guidance
1

Please advice me on a hardware configuration.

I need a circuit that detects a bluetooth device.
ANY device, without the need to pair. Detection status should result in a true or false signal to an Arduino. Based on detecting a BT device or losing the BT device signal I will trigger actions in the Arduino.

What hardware should be able to give a treu or false BT present signal?

2

A quick Google search on;

arduino list bluetooth devices

Suggests that a HC-05 has a command that lists visible Bluetooth devices, so no list, no devices.