I make BusKill laptop kill cords that make your computer lock, shutdown, or self-destruct if the device is physically separated from you.
This protects your (encrypted) data from theft, which can be useful for digital nomads and cryptotraders working in cafes/coworking spaces. But our target audience is journalists, activists, and human rights workers in oppressive regimes.
Both the hardware and the software are open-source (CC-BY-SA, GPLv3). We manufacture the hardware with injection molding, but if you have a 3D-printer, then you can take a stab at our 3D-printable prototype.