Please note that the only Simulink example we have so far is for the PhidgetInterfaceKit. If you wish to use other Phidgets with Simulink, you will have to create an object of that particular type. Details on how to do this is written in the Getting Started Guide for Simulink.
Lastly, the reason why pressing "Apply" gives you an error message when entering a serial number could be because you are not loading the Phidget21 library.
From your modified PhidgetInterfaceKit.m, you have
You should change this to: