15 years ago, I ever installed an application on my Symbian cellphone. That application:
- can detect any GSM cellphone signals,
- will list all GSM signal (it written as id on this app like mac address) which is discoverable / in range with my phone.
- once I select one of them, I can get the proximity where is the selected signal transmitter (in this case, cellphone) might be.
Does this kind of application is still available today on Android?