What does your dead man's switch do?

LqdEngineer writes: "How many of the Slashdot crowd use or have used a Dead Man's Switch designed to perform some action if you don't check in for a certain amount of time? Recently, I decided to put one together using MySQL and some Cron jobs, but I wanted to see what others have their Switches set up to do in the event you fail to check in. E-mails to loved ones? Send encryption keys to friends/family? Hate mail to your boss? Has anyone ever been on the receiving end of a Dead Man's e-mail? I can't even imagine how creepy that would feel."