I made a thing called Wellness Ping because someone I care about went silent and it took too long for anyone to notice.
You get regular check-ins via email. If you don't respond, your emergency contacts get notified.
Built it for anyone who might go missing and needs someone to notice: activists, journalists, researchers, solo folks.
I paid for premium hosting (high-reliability VPS in Sweden) and a quality email provider because uptime actually matters for something like this. Also paying extra for minimal data retention (7 days email activity, working toward zero content storage).
Free forever (as long as I'm alive) and open source.