Nicholas Felton is famous for his gorgeous annual reports on his personal life. I was excited a few weeks back to hear that he'd partnered with Ryan Case to release a free iPhone app to help you track events in your own life: Daytum.
Unfortunately, the app is still so buggy that I gave up using it just a few days after installing it. I'd add events to find they had either cloned themselves or committed suicide by the next morning, and removing duplicate events sometimes caused both the original and the clone to evaporate. It's already a burden to track events in one's life; having to then clean up after the app's whims is a nonstarter.
Good idea, solid visual design, but reliability? Not so much. Maybe in the next update.