as one of the many in this world that has more access to information then i know what to do with, I think an application that you would prevent access to certain other applications for a set period of time. I picture it as basically a toolbar button and a preference file. The preference would define a task, say writing, then let you assign a period of time, say four hours, and would prevent you from using any applications that you have not specified for that task. Advanced forms could let you only access one set of urls in a browser and block others. The toolbar button would let you pulldown a list of tasks, choose one, then close everything other than the defined apps and put a clock in the corner of the screen with a countdown timer.
This could also be handy in teaching computer labs and similar situations.
I personally would find this useful, it is more or less a ‘do not disturb’ sign for our own mind.