Asklemmy

Well, you'd need to send a message to some people that you know would care, when you die or are kidnapped.

There are plenty of services for sending any sort of message.

You'll send the data with a private key and hand out the paired public key before you die. That way any tampering with the data will be obvious to the receiver.

I'd just send a link to the data. For example store the data on Proton drive with a share link.

Now you'd need to detect that you're dead or kidnapped. You could have a timer of say a week or a month, and whenever an email or message is received it resets it. You could also send a warning message to yourself before it goes off, so you have a chance to deal with errors such as an email not arriving.

You'd need a 2nd service to check if the main service is running. Or perhaps it just replies once you send it a message once a day or week or month.

You'd also have to make sure that your reset message to the service is secured. Most likely it will be as long as it isn't absolutely obvious, like you japping on about it at work. But one idea would be to use a proton mail address and keep a pin lock on the app. If you want to go the extra mile the email should also contain something only you can know.

Quite frankly I don't think they'd even expect you to have any such system set up and they wouldn't hack you before you're dead. But maybe I'm wrong. If you really suspect that you'd need someone who is specialized in infosec.

I'd say go look for an existing service that can do this entirely via email, I'd bet it exists already. Otherwise you need to be able to code a bit or find a coder.