Cory Doctorow writes:
[…] This gave me an idea for a more general service: a dead man’s switch to help fight back in the war on security. This service would allow you to register a URL by requesting a message from it, appending your own public key to it and posting it to that URL.
Once you’re registered, you tell the dead man’s switch how often you plan on notifying it that you have not received a secret order, expressed in hours. Thereafter, the service sits there, quietly sending a random number to you at your specified interval, which you sign and send back as a “No secret orders yet” message. If you miss an update, it publishes that fact to an RSS feed.
Read more on The Guardian.