BusKill - A clip on device that when disconnected from a computer will trigger a fail safe event on the computer, such as locking the computer, shutting down, or any script you care for. Totally open source, both hardware and software.

If your a digital nomad or use a computer in public, this might be of interest.

https://www.buskill.in/ https://github.com/BusKill

You can even build it yourself

https://docs.buskill.in/buskill-app/en/stable/hardware_dev/bom.html

If you want to purchase a prebuilt model, they do accept crypto!