"Users of Gmail, Google's email system, can now activate a new feature called Mail Goggles.

It requires an emailer to solve a few easy maths problems quickly before hitting the "send" button. The service is set by default to come into force only on weekend nights, although the settings can be changed.

Google's theory is that if your mental faculties are sufficiently intact to answer the questions, you will have been composed enough to be aware of the consequences of whatever you have just typed."

http://www.telegraph.co.uk/news/3155051/Gmail-offers-Google-goggles-to-avoid-late-night-drunken-emails.html