Alarms & Clock од Luis Miguel

This addon shows a big clock an date in you default new tab. Also, allows to configure different alarms that are fired with red and yellow colors alternate and alarm sound (if you want) during 5 seconds. The alarms are fired inclusive when the tab of clock is closed.

In the side configuration panel, you can set different alarms, which will remain stored even if you close the browser. Just select an hour and minute and save the alarm, easy!

You can configure an url for each alarm, that will be open in new tab when the alarm is fired.

Also, in this panel, you can set the background color to display. In the right part of the time/date, you have a bar to modify the font size.

The on/off sound is configured in the panel of toolbar button. You will see a switch.