Ability to mark tasks as started with one click. and Finish with a second click. I would help keep track of what I am currently working on!
Perhaps one click would change the colour of the task.
App:
Many times, there are quite a few tasks I have planned for 1 day. Usually each task will take quite some time to complete and may not be completed in one sitting (perhaps 1-4 days to complete). With so many tasks to manage it would be enormously helpful to be able to see which tasks I have started on and ones I have not touched because the two are very different. I can see this in use with students with long assignments, in the workplace with projects and at home. It helps with long term plans. For example, a student has an essay due on friday and start on monday. Because there is no way to show it has been started, the task will carry over everyday until it is complete. Even when it is 90% complete it will look the same as an assignment that has not been started, when really one should be able to distinguish tasks at a glance.