I bought this ingenious device from a Kickstarter, and they delivered wicked fast.
It's a decent sized Cookie Jar that will lock away for any period of time, from 1 minute to 1 week. It uses a pair of AA batteries for the lock and display, and more importantly, they can be changed when the device is locked!
Their customer support is amazing (one of the founders handled customer support, and immediatly sent me a replacement for one that arrived broken), and it just works great! As you can see in the above embedded picture, I've got until tomorrow before I can snack on my candy and sweets. This really helps with my personal willpower, and my (very bad) habit of eating poorly most of the time. With my sweets locked in my safe, there is no temptation to snack throughout the day.