It is true that most any hyper dog can set off a motion detector, including the wireless, infrared types that are designed for certain sizes of animals.  Thus, they can inhibit a security system from doing it's job.  But, these 4 footed mobile burglar alarms are still a great type of protection. Since a criminal likes to be in a home in 15 seconds or less, any loud barking dog is a deterrent and can chase even the most surly criminal away. Of course larger dogs that look mean would most likely scare a criminal off better that a tiny yippy dog, but, the smaller furry fellow can sound the alarm and keep most any burglar at bay. Many times thieves go from home to home looking for open doors or windows and their presence can easily set off Fido and get him howling. The point is to keep the criminal from trying to go into your premises in the first place and an alert, barking, indoor dog will help keep them away.