Alarm and countdown timer.
Alarm Ninja sounds an alarm and shows a popup after a specified time period.
Either insert minutes/seconds, or insert the time (24-hour clock) you want the alarm to trigger. Options page makes it possible to control volume and choose between a selection of alarm sounds. It is also possible to disable the popup and just have sound.
Use this extension to prevent overcooked potatoes, burnt pizzas and forgotten appointments. The popup badge shows how many minutes left.