Yesterday I was notified of this little neat project:
github.com/encharm/libsystemtray
(And yes its author would be very happy about feedback patches and so on 😉

Basically it’s a pure C++ library with very few dependencies that implements the support for StatusNotifierItem enabling systemtray icons in KDE Plasma 5 and Ubuntu Unity.
recomonded to be used by C++ applications that don’t actually depend from Qt or GTK and want to keep their dependency footprint very small (it’s Mit licensed so should be ok to use it from an app based on any license)
So now there are officially no excuse to not use our new shiny system tray 😉