Steve, thanks for your question about the Cat Stop maybe bothering animals in the neighbor's yard. 

I'm not sure if that would be a problem. You can shield the high pitch beam somewhat. Or, since you have a small yard, you might place the unit at the edge of your property pointing BACK TOWARDS YOUR YARD (away from the neighbor's yard) if it turns out to be a problem.

 I, too, have animals in the next yard and worried about the dogs howling or being affected by the Cat Stop but they never seemed bothered by it (though I probably have a bigger yard and also pointed the unit  somewhat in a different direction.

I have used the Cat Stop but ultimately have been disappointed with it. It seems to work sporadically. It worked at first but then the "problem cat" seemed to get used to it and would ignore it.   

I'd recommend the Scarecrow sprinkler unit (though it, too, uses a motion detector, it doesn't put out the high pitch sound as a deterrent--it just turns on the sprinkler briefly.)  But that doesn't do you any good in the winter months.  (It's made by the same company.)

My suggestion is to go ahead and buy the Cat Stop and if it doesn't work for your purposes, return it for a refund.  I've found the customer service at the manufacturer to be excellent.  Or, you may call and ask if you can trade up to the Scarecrow unit.  

Good luck.
Hope 2010 will be a cat-free yard for you.
MJ

Over a week ago I put in the motion-activated device which emits a high-pitched sound (higher than we humans can hear) which is supposed to deter cats. First, it startles them when they set off the motion-detector (which also uses their body heat to sense them.)   I was pretty skeptical that this would work but I haven't seen the particular nuisance cat near my pond since I put up the device.  It's green and fits right in with the ivy around the pond. 

I chose this device over the Scarecrow motion-activated water sprinkler cat-deterrent because I wanted something I could use all year round. Plus, I didn't want to risk leaving the hose turned on all the time because it leaks very slightly at the faucet. That would have been a waste of water until I get the faucet fixed. 

Will keep you posted on how well it seems to be working.   M.J.