There is a big brother aspect to the new Google application Mail Goggles that makes us a bit wary, and yet...wow would it ever have come in useful on more than one occasion we've since tried to forget. Per the GMail blog:

Sometimes I send messages I shouldn't send...Gmail can't always prevent you from sending messages you might later regret, but today we're launching a new Labs feature I wrote called Mail Goggles which may help.

When you enable Mail Goggles, it will check that you're really sure you want to send that late night Friday email. And what better way to check than by making you solve a few simple math problems after you click send to verify you're in the right state of mind?

By default, Mail Goggles is only active late night on the weekend as that is the time you're most likely to need it. Once enabled, you can adjust when it's active in the General settings.