We recently heard of an electronic bark controller that emits a sonic scream whenever the dog barks. HAve just imported one from USA so will report back on it when we figure out how to work it.
It sort of buzzs the ear drums so dog stops barking. It is a sender unit that sits somewhere safe and if the dog barks within something like 100mts it buzzs them. (depends on the unit)
No shock. no pain. No collars. Pretty sure that won't be banned in NSW.
I just did a google search for Sonic Bark Stop and came up with lots of different ones.
Border River Pet Resort