This is a simple example of monitoring Bluetooth-related data over DBus using Bluez on Linux.
Access to the DBus interface comes as standard in gio, which is easily available via apt, e.g.:
sudo apt install libgio3.0-cil-dev
The code can be built using g++ and pkg-config, e.g.:
g++ -std=c++14 -Wall -Wextra -pedantic -O2 $(pkg-config --cflags gio-2.0) example.cpp DBusBluez.cpp $(pkg-config --libs gio-2.0) -o bluez
The example program will listen for ObjectManager messages for an optional period until quitting (e.g., ./a.out 10 will run for 10 seconds and then quit). If no period is specified, the program runs continually until interrupted.