setInterval( function () {
widget.showNotification('test!')
}, 15000 );
This shows notification every 15 seconds.
(You don't need to put it inside of request or window.onload).
Auto-reloading and timers
Be warned that if you use Debug Mode in Uniteness (or maybe Reset in Yusef), which automatically reloads scripts on each request - this will pile up. I.e. old timers are not deleted and you might end up having dozens of timers working simultaneously.
This can be called "crontab", "cron", "timer" in other applications.