I thought that this was pretty funny! Yoinked from CNet:
Just a quick post to mention a silly (or is it?) experiment that Google has released to the public: Mail Goggles. This feature is designed to prevent you from sending stupid e-mails in the small hours, when you’re most likely to be inebriated and at risk of making a complete idiot of yourself.
When enabled, Mail Goggles kicks in at the time you specify (default is between 10 p.m. and 4 a.m. on Friday and Saturday), and throws five math problems up on the screen when you press “send.” You have a limited period of time to solve them. If you can answer the questions, presumably you’re of mind sound enough to tell off your boss, or pour your heart out to your ex-lover.
If you can solve simple math problems even when under the table, there’s an option to ramp up the difficulty of the questions, but sadly they remain in the arithmetic realm and don’t drift into interesting algebra or calculus.
To activate Mail Goggles, go into Gmail’s settings, and turn on Mail Goggles in the “Labs” tab. Then adjust how and when it works in the “General” tab.