In 2009 I was employed in a corporate and had "trust based" working hours. I really liked that as it gave me a lot of flexibility in structuring my day and my work. As you usually do not work less, but more with that kind of freedom, I felt the need to track my hours.
First (around the end of 2007), I developed a simple web-version of WorkTimes as that was the only way to have "apps" on the iPhone in those days. After the announcement of the "real" App Store I immediately started working on WorkTimes for iPhone.
Finally, on November, 9th 2009 I released Version 1.0 to the App Store.