This extension reminds you to take a break from work.
Scientists have found that sitting for long hours can have negative effects on health. To prevent these negative effect it is recommended to stand up every hour.
This extension let you setup an interval timer to remind you to stand up.
To learn more about this problem read this lifehacker article: http://lifehacker.com/5879536/how-sitting-all-day-is-damaging-your-body-and-how-you-can-counteract-it