I haven't tried this but I really want to. I've noticed that I'm most productive when I'm working on the laptop and I don't have anywhere to plug in. I hover over the battery icon and notice that I only have an hour left... and I work like crazy. Motivation levels are high and there's no procrastination. I usually get my task done, too.

I wonder if the effect will be the same if the time limit is artificial and planned. I also wonder how much discipline it takes to make it work. Only one way to find out, I suppose.