Many years ago, my mother's cousin lost her husband unexpectedly. They lived in a very isolated, rural area. She was concerned about being alone, so she called the local sheriff's office and asked if they would do a consultation to tell her what kind of security system she needed. The guy came out, looked around and said "to be honest, it doesn't matter what kind of system you put in, it would still take us 20 minutes at best to get to you if it went off." He then pointed to her dog and said that he was the best security system she could possibly have.
Since the dog was getting older, she went the next day and got a second one as a "backup." She also got her concealed carry license, which she thankfully never had to put to use. Thieves don't like noise and they don't like the possibility of getting bitten.