Write or Die is perhaps the greatest writing "aid" ever devised and put into use. It punishes you for not writing using many methods, all of which are quite motivating. The idea here is that tangible punishment is more effective than intangible (and unlikely) happiness experienced upon finishing your great American novel.
And it is effective. There are three modes to choose from, the worst being Kamikaze mode. Contrary to what you may believe, suicide bombers will not come "sharking" through the air, towards your house. No. Your words merely commit suicide and unwrite themselves. (And also, the screen turns an angry red, which always frightens me.)
There's a bunch of settings you can change, including "grace period", word goal, and total time allotted for writing. All in all, it's a very nice little motivator. And the web app is free: http://writeordie.com/#Web+App
However, the entire idea of Write or Die implies that you actually want to get words on paper. But what if you've lost all hope for your novel and have just given up? Then, words extirpating themselves from your paper may not seem so troubling.
So there should be something new, something like an "Actually Write or Die" where the punishments are not reductions in word count or annoying noises or little pop-ups. Those are annoying, but somewhat bearable, especially if you truly lack motivation. The punishments should be painful. So painful that you absolutely must meet your word count.
Ideas for punishments:
-Automated sending of embarrassing and somewhat stalkerish emails to friends, family, and teachers.
-Hard drive implosion after a minute of inactivity.
-Playing of Sufjan Stevens' Age of Adz at incredibly high volume in noise-canceling earbuds.
-Actual Kamikaze mode involving actual suicide bombers.
-Your monitor will self-destruct after 10 seconds of inactivity.
But for now, Write or Die will have to do. It's nice. It's very nice. Try it. It's free.