You don't always need notifications on. Whether you need to get some work done or you don't like the fact your iPhone beeps and vibrates when you're on the phone, DoNotDisturb is a simple tweak for jailbroken iPhones that adds a single button that blocks all notifications.
DoNotDisturb doesn't do anything else — it just blocks notifications. If you like having notifications enabled while you're at work, but want to cut them out when you get home this is a dead simple way to do it. Just pull down Notification Center, toggle DoNotDisturb on, and you're ready to go. The nice thing about DoNotDisturb is that the badges on the app icons will still add up so when you do go to look at your phone you'll know what you missed right away. You can find DoNotDisturb for free in the ModMyi Repo in Cydia.