nice to have Rated 4 out of 5 stars

you never know when your roomate's going to get back from class ;) icon doesn't show up in toolbar on FF v.15 (which is prolly just my luck with technology and not a real issue) but the F9 key works.

This review is for a previous version of the add-on (1.5). 

Toolbar button icon

You can add the toolbar button icon by right-clicking on any toolbar in the Firefox browser window, choose Customize, and then drag the Panic Button item to the desired location.