Simple script that tells me "You've been on Facebook n minutes now, c'mon." when I spend too much time on Facebook.

FbWatch.js

// ==UserScript==
// @name         Facebook watcher
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Makes sure you don't spend too much time on Facebook
// @author       You
// @require      http://coffeescript.org/v1/browser-compiler/coffee-script.js
// @match        https://www.facebook.com/*
// ==/UserScript==

// jshint evil:true

eval(CoffeeScript.compile(`
  secs = 0

  setInterval ->
    secs++

    if secs % 60 is 0
      alert "You've been on Facebook #{secs / 60} minute#{if secs is 60 then '' else 's'} now, c'mon."
  , 1000
`));