RescueTime for Chrome and Chrome OS

RescueTime tracks the time you spend in the currently active tab or window of your browser. This gives you a clear picture of what you were actually doing all day. If you walk away from your computer for a few minutes, RescueTime automatically figures out when you're away and stops tracking. RescueTime does it's best to auto-categorize the sites you visit. It also scores them on a scale from Very Productive to Very Distracting. You can easily fine-tune the defaults to suit your needs. It's also simple to pause RescueTime, or delete any time you'd rather not have tracked.