Recently the number of local moggies has risen - and at least two have become regular habitués of our garden. And most especially, our borders when they have a need for a toilet.
Searching around for an answer, a relative recommended one of the Cat Guard devices. (They suggested a specific one that we have been unable to find.)
I found several ultrasonic devices here:
Any opinions on effectiveness?
The area we need to control is fairly small. Any reason not to go for the cheapest?
In general they seem to be incredibly expensive for a fairly simple set up. (Not just the devices but the mains power supplies.) And I am deeply sceptical as so many devices like this (e.g. against mosquitoes) have been flogged without any proof that they work. And if the noise they make is audible (as some people report), maybe it would annoy us and/or neighbours?