I am looking to build a hardware equipment or device with the following function:
1. When a person carrying a mobile phone is in the vicinity of this device or hardware, it will be able to detect the signal from it and decipher the information from that signal to relay the mobile number of that handset.
2. My understanding is that the information relayed from the mobile phone signal contains the IMSI information which in turn contains the mobile phone number of that handset.
Any information on how to build a device like this will be appreciated.