What Does Your Dead Man's Switch Do?

LqdEngineer asks: "How many of you 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 the results of such a system?"