Anyone who has the dealer installed Code-Alarm (Ford) keyless entry/alarm/remote start, have you ever used an external stick on keypad?

I am looking for input/information on feasibility of adding a stick on keypad to my truck.
This type of keypad is basically a third fob, just one you mount on the truck. That means it must be compatible with the controller for the keyless entry.

The setup I presently have is not compatible with the Code-Alarm (Ford) fob, thus will not work.
I am looking at buying a Code-Alarm system, that will work with the number pad, if it can be bought aftermarket.
Anyone with information or experience with this please let me know what you have found.
Thanks
Chris