This is a TL431 comparator fuse that can be made on a breadboard,pcb or even copper tape. It uses a 1.5V Battery(Can be AA,AAA,C or D). Its used to add 1.5V to the voltage drop across the current sense resistor. This is needed since it can only turn on at 2.5V at the reference pin. The 431 can be found in a lot of switching power supplies, just look for a tiny transistor looking device containing the number 431. This fuse is better than poly fuses and circuit breakers.
Here are some equations for current sense resistor:
$$R_{sense}=\frac{1}{I_{trip}}$$
$$P_{sense}=I_{trip}^2R_{sense}$$
$$V_{max}=\sqrt{R_{sense}P_{sense}}$$
Circuit Simulator