Rated 4 out of 5 stars

As previously said: Does what it claims !
Pops up a short Javascript notice with user-defined text.
Just drag the new toggle-button to your toolbar !
What I miss, is a optional visible countdown. For example a tooltip that shows the remaining time when I hover over the button. Because I use the small icon set, the icon changes are barely noticeable.
Can you alter it that you can have also an actual time as input ? (e.g. 23:15:00)
Going to use it !

This review is for a previous version of the add-on (0.5).