At least from how I have heard it described from actual physiotherapists, Acupuncture is mainly used to cause increases of blood flow and localized swelling to help relieve muscle pain / promote healing (more resources to repair muscle tissue) not something that can be used to see the health of your internal organs.
At my best guess there toy works on the concept of skin impedance,
I love that "Clinically tested" does not mean clinically proven.