What software EOS is using for wifi connectivity? Is this a custom themed NetworkManager? Wpa supplicant? something home made? I am asking about both: the beautiful UI app in the system tray and about the underlying daemon/service that does the actual connection.
Here is the GitHub for the network switchboard plugin https://github.com/elementary/switchboard-plug-network
Here is the indicator (thanks to @jena): https://github.com/elementary/wingpanel-indicator-network
You'll need Vala compiler, Switchboard library, Ninja and other things to compile.