There's actually an excellent Dutch piece of software for this (Windows only though, but works fine in Wine on other platforms): Overhoor [1].
I used it under Windows 3.11 as a child, and kept using it for French and German into my late teens and Windows ME. It is simple, just as this tool. To this day, it's a piece of freeware that gives me good memories of a forgotten era.
Since the author describes learning Dutch, I though I might mention its existence.
I came here to say the same thing! I used an ancient (DOS) version of it to get me through high school French, German, Latin and so on. Fond memories.
The funny thing is: this actually works incredibly well. Perimeter wires are a PITA to install, but once that's done, they are a very practical and flawless method for making sure the robot does not escape into the neighbour's yard or worse. The random movement is really effective too. What exactly can a smart robot do better?
Removing the need for perimeter wires would be great, as long as it works 100% flawlessly. Obstacle detection would also be nice, so I can avoid my mower chewing up the toys my kid sometimes leaves lying around (though it is a great motivation to clean up!)