The CP4 Disaster Prevention kit is exactly what it says. It prevents catastrophic loses in the fuel system. The CP4 has been known to fail when using lower quality fuels or running the fuel system dry, as the diesel is actually a lubricant also. When such failures happen the push which is mechanically driven will create lots of fine metal particles that ultimate contaminate the injectors, fuel lines and fuel tank.
With this kit fitted, if the pump was to fail the remaining parts of the fuel system are safe and will not be contaminated by these metal particles.