ESP32 Module with mobile device proximity

Hi I am planning a project and intend on using ESP32 modules to monitor proximity to a mobile device. This proximity data should be regularly sent to the mobile device and if the distance threshold is broken it will initiate a protocol in the ESP32 hardware housing. I want to make sure this is possible using an ESP32 and any other guidance you folks may have. Also if I should use the Arduino esp32 module or if the much cheaper amazon module with Arduino IDE compatibility would work as well. Thanks!

Seems like all your problems are at the mobile device end. All the ESP needs to do is send out a regular signal and complain if there is no response, which can't be hard.