Agreed nothing worse than when your mower hits a pile of cat shit or the grandkids step in it.
I have had some success with mothballs, or spraying diluted jeyes fluid on the grass. My neighbour has spent £200 on sonic devices which he says is helping. I was thinking of putting carpet gripper on my fence panel tops but would probably end up with the numerous cat households where I live kicking off.
Another neighbour laid down toy rubber snakes but that just scares the shit out of the cats.
What I don't get is that if a dog took a crap on my lawn that would be an offence but cats can just wander and take a dump at their will.