Usage :
itag.init("iTAG"); // BLE Init + name
itag.set_batt( 10 ); // Update battery status
itag.set_btn( 1 ); // Send state to client
This is code has it's roots from the following projects :
Mainly the work done by nkolban, his BLE_notify sketch
https://github.com/nkolban/ESP32_BLE_Arduino
iTag protocol analyze by Thejesh
https://thejeshgn.com/2017/06/20/reverse-engineering-itag-bluetooth-low-energy-button/
sample code for iTag32 made by anik
https://github.com/aknik/ESP32/tree/master/iTag32
The following client software can be used
itracing2
https://github.com/sylvek/itracing2
All tracker
http://www.swalle.com/all-tracker-app-for-the-best-key-finder-in-2018-n169-1.html