One could also upload an encrypted file, and give the password to the people to whom the file is going.

The website is missing the password, and the recipients don't have the file until the website gives it to them.

(Clearly this still isn't (and can't ever be) sufficient though: bribery/threats of violence/blackmail by either party towards the other.)

Perhaps a better method for less trustworthy heirs is to give them half of a worded password. Say the password is "pond elephant evergreen tennis skyscraper electric". You give them "pond elephant evergreen" now (in searchable e-mail), and let the dead man's switch give them "tennis skyscraper electric".

Alternatively, let the dead man's switch alert heirs to swap their half of the password, so that all heirs now have the full password. Then you don't overly depend on the dead man's switch.

That's one of one of the main use cases I had in mind when I wrote this: https://github.com/ryancdotorg/threshcrypt - you encrypt a file using N passwords and require that at least M passwords be presented in order to decrypt. At the moment it's not suitable for non-technical users, though you could make a bootable thumb drive that autoruns it and saves the decrypted file. I was also able to embed it in an initramfs on Debian for use with full disk encryption.

A use case that might make more sense (though would still require trust) could be things like posting messages to Twitter, Blogs, etc. about your death.

Once it earns some trust, it could offer to sell your startup/website/app to someone that would do a good job of maintaining it (or release it as open source).

You are taking it a bit too seriouslly.

As it even notes on the page its 'running on free quota' - hardly something to actully be trusted with life or death information.

A cool tech demo, not a 'premium' service.

Agreed, trust is key for a service like this. Ideally the contents need to be secure, but not so secure that you are the only one who can read them--otherwise what's the point since you're probably abducted or dead?

The point is that I don't want YOU to read this info BEFORE I'm dead. And basically there's no way to prevent that if your website contains everything needed to disclose the information.

Shurely you could just store the decruption key in deadman.io. The actual encrypted files stored elsewhere.

Like you note with your current setup, the passphrase is useless on its own.

Or store encypted file in one deadman.io switch, and the passphrase in another switch (in another account). The evil owner of said website, shouldnt be able to connect the two. (whats the chances they going to arbitarly try decoding every file they have with every passphrase they have)