Can I get a digital out signal when hitting geofence?

Hi,
I have played around with an ardupilot rover about 10 years ago but since left it at that.

Now I might have a new use case:

I have an awesome and well working lawn robot. However he is dumb-dumb. No perimeter wire, no GPS, just run into things and drive backwards, then repeat. As he is awesome at what he does I don´t want to alter him in a way where I would need to take control of movement. So not what ardupilot is usually about.

Unless the garden is set up to cater to this very specific need he just runs off or deep dives down cliffs so I put him on an actual dog restraint and he just mows circles around something heavy that I have to move around every hour.

So I wondered how about I get GPS RTK going and set a couple of exclusion zones in the map of ardupilot. I am looking for hours for information but cannot be certain.

Here goes: Can I get RTK accuracy for making exclusion zones in ardupilot and is there then any way I can just get a digital signal when going into an exclusion zone with RTK accuracy using Ardupilot not using any of the other functionality or do I need to look elsewhere? As Sean Connery in Hunt for Red October has put it, just give me one ping is all I need. That I would then feed into the signal for replicating the run into stuff sensor and would make him turn away and would make it even more awesomer.