Mail Goggles

According to http://arstechnica.com/news.ars/post/20081007-mail-goggles-a-breathlyzer-test-for-your-gmail.html, Gmail has a new feature to protect against the email equivalent of drunk dialing.

Called "Mail Goggles," the Gmail add-on makes sending e-mail from Gmail more difficult during certain times that you can set manually (while sober, that is). How does it do this? If you have Mail Goggles installed—which you can do by going to the "Labs" tab under your Gmail settings and turning them on—it will force you to answer a series of math questions before sending out any new messages.

If you get the math questions wrong, or take too long, you receive a message telling you to go to bed, and your email is saved until a sober decision can be made.