A dog can be your best friend when it comes to home security.
Burglar alarms are not the be-all and end-all of home security. There are plenty of other things you can install in your home that will help to stop a burglar from gaining entry and many of them are very simple and inexpensive.
The key is to secure the possible points of entry. This means that doors should be made of strong, solid material (definitely not plastic or glass), be properly secured to their hinges and have tamper-resistant locks. Ideally, you should have an extra deadbolt that you put on at night, made from very strong metal.
Windows should be made from toughened glass, preferably double-glazed, so that they are almost impossible to break. Although window locks are relatively uncommon, they help greatly with security, and you should consider installing them. If your house has windows in a position where they can be easily and discreetly accessed from the street, such as basement windows, you should consider putting metal bars on them.
It is also important for your garden to be secure, as far more burglars enter through the back of your house than the front. This means that...