As far as I know, no such API exists to call libnotify from a QML component. 

To avoid creating a C++ plugin just to get notifications for a desktop application, I would use pyotherside to call a small python module to do the job:

Prerequisite:

Install pyotherside: sudo ap-get install pyotherside

First the QML:

import QtQuick 2.0 import Ubuntu. Components 1.1 import io.thp.pyotherside 1.2 Rectangle { width: 200 height: 200 Button { text: "press" anchors.centerIn: parent onClicked: { py.call('notify.pressme', [], function() {}); } } Python { id: py Component.onCompleted: { addImportPath(Qt.resolvedUrl('.'));  importModule('notify', function() {}); } } }

And the python code (keep both in the same directory), a file named notify.py :

#! /usr/bin/env python3 import subprocess def pressme(): subprocess.call(["notify-send", "hello", "world"])

After pressing the QML Button, you'll get a notification like this one:

Please read the notify-send man page for further options.