A jumping, punching, kung fu-trained robot that protects your house and family—what could go wrong?

A hooded man with a knife walks toward a woman sitting in her backyard. Before he reaches her, a humanoid robot steps between them and squares up. That’s the money shot in the one-minute video Unitree released on October 21 to introduce the H2-X, aka “Kung Fu Legend Guardian.” It’s a machine that, in the company’s words, offers “powerful performance to serve and guard you.” It’s a robot that a lot of people will want at home: the T-800 to their John...