Pet Containment Possible To Build A Transmitter For A "invisible Fence" Type Wireless Pet Containment System?

Possible to build a transmitter for a "invisible fence" type wireless pet containment system? - pet containment

I have a model from Innotek, I will keep my cat in the house. These things are expensive and do not think the model is an optional remote control. Optionally, you can also purchase "hard" channel, but are "always on" type device to control size. Is it possible to build a remote control? I think that like the construction of a transmitter would be of something like a garage door, etc. Please help!