Contrary to what most people here have said, I believe there is a use for such a service. However you would have to focus on a niche. Lawyers time their tasks - they bill by increments as short as 6 minutes. To be useful for lawyers you would have to add more features. A few that come to mind would be having multiple connected timers (starting one stops whatever other one is running), labels associated with the timers, notes associated with the timers, and a whole lot of security. Current timer solutions for lawyers are all desktop applications, so a web based solution could be interesting.