Gone Man’s Switch is a simple web application that allows you to create messages that will be delivered by email when you are absent (gone) for a certain period, AKA a dead man’s switch.
It is a free self-hosted alternative to deadmansswitch.net. It doesn’t have as many features, but it does the job.
More info in the GitHub repo: https://github.com/jhonderson/gone-man-switch
the only issue I can foresee about such a service is how to guarantee privacy. since most of the info to be passed along is likely to be of a sensitive nature