Is there a browser plug-in that will warn the user ever X seconds with a popup and/or audio alarm when they are browsing predefined sites? Example: I go to Facebook and get sucked in and before I realized it 10 minutes has passed. I'd like an alarm to go off every 30 seconds on this site to tell me to get-out-of-there.
If you use Chrome, try the StayFocusd extension.
If you're a Firefox user, use the Leech Block add-on.
I think the plugin for Chrome is a better plugin overall.