Tasks and calendar items - what I'd like

I really do spend too much time thinking about tasks, calendars, projects and the like. It recently occurred to me that I would like to see support for something that's a hybrid between a task and an appointment.

You could think of it as a task that has a date, time and span. Or you could think of it as an appointment that shows up on a task list and has a priority/urgency attribute.

The idea is that I'd schedule it as an appointment and it would show up in my task list. If I deleted the appointment I'd have the option of deleting the task, or just editing the task. If I deleted the task then I'd delete the appointment. Completing the task would leave the appointment untouched.

If I see anything like that I'll attach a note here.