Well. If you happen to be going into a high-profile meeting with a mob boss and you happen to have incriminating documents about him, upload them to Deadman and hopefully you will get out alive. :)

More seriously, I think the core technology would be useful for elderly, people going on hikes into remote areas, etc.

Better yet, retain a lawyer for this purpose. The difference being that the lawyer can make determinations this site cannot. For example, you might think that a one week period is sufficient however you'd be better off with a one month period just for safety reasons as you might be stuck on some mountain or locked up with some mob boss for a week and you don't want the dead man's switch to trigger. But what if you're coming home from the mountain climbing trip or the meeting with the mob boss and you get in a car accident and in order to relieve brain swelling, doctors have you in a medically-induced coma for six weeks? Oops...

A lawyer can make such a judgment call without falling back to the binary decision of "has the time elapsed with no check-in?".

But for that use case, I have to tell the mob boss that I uploaded a secret to deadman.io. At which point he takes out his rubber hose collection, and gently persuades me to log in and delete the secret.

You don't need to tell where, and you can use a one-off generated password that you really didn't memorize.

A) The idea is that the "rubber hose collection" leads to you revealing where it is, and B) if it's a generated password, how will you stop the deadman's switch in the event of getting away?

You ping the service by email/phone/SMS, not by logging in. But you have a point, you'd have to keep pinging it for the rest of your life and it would fire anyway when you die :)

Not necessarily.

You could say, I have a bunch of documents that implicate you and they'll be sent out to authorities should I not answer my email or phone at N time.

"I know you really don't want to tell me where those documents are, but maybe you'll tell my friend, Mr. Hosey?"

Maybe, but this is the case for any dead man's switch (even a bank/lawyer). It's always a balance between what the mob boss thinks he can get you to do vs the power of the dirt you have on him. Literature/TV have beaten to death the permutations/twists on this theme.

I set it up to check an old email account I tend to forget about for months at a time (which can't auto-forward mail). I could set a calendar event, but I don't want to force myself to check it at exact intervals.

There's a web-hook switch which is intriguing, though I haven't come up with a good use case yet.