WeExpire's motto is Simpler than a will; safer than a note. Basically, it's an open-source tool for creating emergency notes that can be read by your trusted contacts only after your death or if you are seriously injured.
How does it work? You create a note and choose an "I'm alive" window. It gives you a unique QR Code. You pass that to the intended reader. When they scan it, the system sends you an email with a link to click. If you don't click it within the "I'm alive" window, the intended reader gains access to your note. You're alive? Click the link and they don't get access.
Smart. Not sure it's legally binding, but smart.